Taking out the factors of the given numbers,

$36 = 2 \times 2 \times 3 \times 3$
$72 = 2 \times 2 \times 2 \times 3 \times 3$
$\therefore $ L.C.M of $36$  and $72$  $= 2 \times 2 \times 2 \times 3 \times 3 = 72$

Multiples of $ 18 = 18, 36, 54...$
Multiples of $ 6 = 6, 12, 18, ... $
The first common multiple will be $ 18 $
And the next common multiples will be multiples of $ 18 $
Hence, first three common multiples of $ 18, 6 $ are $ 18, 36, 54 $

Factors of the given numbers are,

Factors are $ 17 = 1 \times 17$
$5 = 1 \times 5 $
$\therefore $ LCM of $17$ and $5$  $= 1 \times 17 \times 5 = 85$

LCM of two co -prime numbers is their product.
Example: Consider $6$ and $7,$
Multiple of $6$ $ = 6,12,18,24,30,36,42, 48$
Multiple of $7$ $= 7,14,21,28,35,42$
L.C.M of $6$ and $7$ $= 42$
The product of $6$ and $7$ $= 6 \times 7 = 42$

$12\times 1=12$
$12\times 3=36$
$\therefore 12$ and $36$ are multiples,

Multiples of $14$ are $14\times 1, 14\times 2$ ....
And $7$ and $1$ are the factors of $14$.

$LCM \times HCF =$ product of numbers

$p = 4, 4\div 2 = 2$
$p + 2 = 4 +2, 6\div 2 = 3$
$p + 4 = 4 + 4, 8\div 2 = 4$
Product is divisible by $2.$
Therefore, $C$ is the correct answer.

$3$ is not a positive multiple of $12$ as it is smaller than $12$.
Rest others are multiples of $12$.

Multiples of $ 3 = 3, 6, 9, 12, 15, 18.. $
Multiples of $ 4 = 4, 8, 12, 16, 20.. $

The first common multiple will be $ 12 $

And the next common multiples will be multiples of $ 12 $

Hence, first four common multiples of $ 3, 4 $ are $ 12, 24, 36, 48 $

Multiples of $ 3 = 3, 6, 9, 12, 15, 18.. $
Multiples of $ 4 = 4, 8, 12, 16, 20.. $

Multiples of $ 6 = 6, 12, 18, 36.. $ 

The first common multiple will be $ 12 $

And the next common multiples will be multiples of $ 12 $

Hence, first four common multiples of $ 3, 4, 6 $ are $ 12, 24, 36, 48 $

First six multiples of  $ 13 = 13\times 1+13\times 2+13\times 3+13\times 4+13\times 5+13\times 6$

Multiples of $ 8 = 8, 16, 24, 32, .. $
Multiples of $ 12 = 12, 24, 36, 48... $

The first common multiple will be $ 24 $

And the next common multiples will be multiples of $ 24 $

Hence, first four common multiples of $ 8, 12 $ are $ 24, 48, 72, 96  $

First six multiples of $ 17 =  17, 34, 51, 68, 85$ and $102. $

LCM of A and B is B it means that B is multiple of A. LCM of B and C is C it means C is multiple of B or we can say that C is multiple of A also.

first five multiple of 6 are 

Number which has a multiple of all the numbers from 1 to 10 will be multiple of their LCM.

LCM of 9,10,12

$10=2\times5$
$20=2^2\times 5$

Since on dividing by $3$ the remainder is $1$, the sum of digits of the number must add upto a number, dividing which by $3$ we get remainder $1$

Let the divisor be $a$ and remainder be $r$

The numbers $2,4,6,8,10$ are known as even number.