A necessary truth is a statement that is true in all possible worlds. The statement 'All bachelors are unmarried' is true in all possible worlds because it is a tautology, meaning that it is true by definition.

A contingent truth is a statement that is true in some possible worlds but not in others. The statement 'The sky is blue' is true in some possible worlds (e.g., our world) but not in others (e.g., a world where the sky is red).

The statement '2 + 2 = 4' is a necessary truth because it is true in all possible worlds. This is because the concept of addition is defined in such a way that 2 + 2 will always equal 4.

The statement 'The Earth is round' is a contingent truth because it is not true in all possible worlds. For example, it is possible to imagine a world in which the Earth is flat.

The statement 'All dogs are mammals' is a necessary truth because it is true in all possible worlds. This is because the concept of a dog is defined as a type of mammal.

The statement 'All birds can fly' is a contingent truth because it is not true in all possible worlds. For example, it is possible to imagine a world in which some birds cannot fly, such as penguins.

The statement 'The past cannot be changed' is a necessary truth because it is true in all possible worlds. This is because the concept of time is defined in such a way that the past is always fixed and cannot be altered.

The statement 'The future is uncertain' is a contingent truth because it is not true in all possible worlds. For example, it is possible to imagine a world in which the future is completely predictable.

None of the above statements is a necessary truth because they are all contingent truths. The existence or non-existence of God, the infinity or finitude of the universe, and other similar statements are all matters of belief and cannot be proven or disproven with certainty.

All of the above statements are contingent truths because they are all matters of belief and cannot be proven or disproven with certainty.

The statement 'I think, therefore I am' is a necessary truth because it is true in all possible worlds. This is because the concept of thinking is defined in such a way that it implies existence.

The statement 'The world is real' is a contingent truth because it is not true in all possible worlds. For example, it is possible to imagine a world in which the world is not real, such as a dream world.

None of the above statements is a necessary truth because they are all contingent truths. The nature of beauty, morality, values, and truth are all matters of opinion and cannot be proven or disproven with certainty.

All of the above statements are contingent truths because they are all matters of opinion and cannot be proven or disproven with certainty.

The statement 'The laws of physics are universal' is a necessary truth because it is true in all possible worlds. This is because the laws of physics are defined as the fundamental principles that govern the behavior of the universe, and these principles are the same in all possible worlds.