First we need to find the the answer to both the square root of 49 and 9.
The "square root" is a term referring to a number, multiplied by itself (x • x) would be = to your square root.
So for example: Square root of 16 = 4 because 4*4=16
So lets get out numbers:


Now you multiply 3*7 (or 7*3) and you get 21.
Final answer: 21
Ask your parents about it if they didn't help you can copy mine,
Well I asked my parents about they told me that around their age there weren't lots of facilities they even rarely saw transportation facilities like cars and bikes there were no proper internet facilities e.t.c
When I said them what were the changes in the last 25 years they said there were drastic changes including social, economic, science, transportation, health e.t.c and many more
So the answer is D hope this would help you