LH is the hormone that is not secreted by human placenta. It is secreted by anterior pituitary. Initially during pregnancy, hCG performs the function of LH of maintaining corpus luteum for the secretion of progesterone. Later (around 16th week) in pregnancy, when placenta itself starts secreting estrogen and progesterone, corpus luteum regresses.

Flower is a reproductive organ. Essential parts of a flower include the stamens (male parts) and the carpels (female parts). It takes part in the process of pollination which results into the completion of reproduction. Pollen grains transfer from anther to carpel resulting into the formation of seeds and fruit.

Asteraceae or Composite is large and it is an economically important family of flowering plants. In Asteraceae, the flowers are bracteates, sessile, complete (flower having calyx, corolla, stamens, and pistil) As well as hermaphrodite (i.e. bisexual), pentamerous (i.e. calyx, corolla, androecium, and gynoecium), actinomorphic i.e. radial symmetry, and epigynous ovary enclosed in the receptacle with stamens. So, the correct answer is ‘Flowers are hypogynous in Asteraceae’.

So option B is correct.

Flowers are used by the plants for sexual reproduction. Actually, every single part of a flower is used only for reproduction. Flowers care about making themselves beautiful for one purpose to attract a mate, and hence to reproduce.

The correct answer is B.

The flower is a reproductive organ of an angiosperm plant. The typical flowers consist of sepals, petals, stamens, and carpels. A flower having both stamens as well as carpels or pistils is known as a bisexual flower. Flowers that are either staminate (means having stamens) or pistillate (having pistils only) are known as unisexual flowers. Thus the answer is unisexual flowers.

The correct option is B.

• Anthocyanins are red or purple colored water-soluble pigments present in the plant cell vacuoles. 
• They are responsible for the color of the flowers, fruits as well as leaves. But, phycoerythrin is a photosynthetic pigment and it is found in red algae.
• Carotenes and Xanthophylls both are carotenoid pigments of higher plants. They are accessory photosynthetic pigments.
• The correct option is C.

Most of the night flowers are white emerges better in low light conditions. Hence making it simpler for insects to discover. As they bloom at night the plant does not have to waste resources producing coloured pigments to attract the day insects. Night blossoming blooms are ordinarily and vigorously scented. Then it goes about as an attractant for nighttime insects and mammals.

Thus the correct answer is option D.

Vallisneria is a submerged hydrophyte and it is a dioecious plant with the flowers borne under the water. The male flowers detach on the maturity and float on the surface of the water whereas the female flowers grow under the water. They come up to the surface with the help of their thin long stalk. 

The male flowers of Vallisneria are floating on the surface of the water, with the help of two tepals forming boat-shaped float while the third smaller one functions as a rudder.

So, the correct answer is D.

Epipetalous is the condition of having the stamens attached to the petals.

The epicalyx is the additional whorl made up of involucre that is places exterior to the whorl of the calyx. It is found in Hibiscus rosa-sinensis.

The flowers belonging to the family Malvaceae have a number of bracteoles that can vary from three bracteoles to many bracteoles. These bracteoles form a whorl of epicalyx below the calyx. So, epicalyx becomes the outermost accessory whorl. It can be seen in China Rose. 

When the petals of the corolla are not fused and are free, the condition is called polypetalous. 

Solanum nigrum belongs to the family Solanaceae. It has fused petals called gamopetalous conditon. The Corolla looks wheel-shaped and is called rotate.

The corolla can have different shapes when the petals show fusion or the gamopetalous condition. The funnel-shaped corolla is called infundibulum.

Stigma is the terminal receptive part of the pistil which functions as landing platform for the pollen grains. It also determines the compatibility of the pollen grains.

The anthers of stamens can be found facing the centre or the periphery of the flowers. When the anthers face the centre or the gynoecium and dehisce longitudinally while facing the carpel or gynoecium, the condition is called introrse. When the anthers face the periphery or the petals and dehisce away from the carpel, the condition is called extrorse.