I need help with this please

The fourth one.

Step-by-step explanation:

By process of elimination, the fourth one is right. First of all, 1st one can't be right because 1 and 2 aren't even the same shape and/or size when they translate, so that can't be it. 2nd one isn't it either because once again, 1 and 3 aren't the same shape and/or size, no matter how much you rotate or move. 3rd one isn't it because while they do translate 6 down, they aren't the same shape since they are both rotated differently, so 3rd one isn't it. Fourth one is it because a reflection can be seen if you do it mentally. If you rotate 2 upside down and compare that to 3, it will be the same shape and translates 6 down like the 4th answer says.

i'm assuming it's looking for the missing length, which should be 4cm

hope this !

step-by-step explanation: