Answer:
C
Step-by-step explanation:
√45 is irrational, so to approximate where it goes on the number line, you should find the closest squares to it, which are 36 and 49. These numbers are the squares of 6 and 7, so √45 can't be A, B, or D, as none of them are between 6 and 7. Only C is, and as √45 is closer to √49 than √36, it should be closer to 7 in the number line, but still in between both of them.
Hope this helps !! :D