The answer is option A, 4.5 inches.
This is because the smallest unit on the ruler is half an inch. We can’t assume that the green tape is stopping at a more exact point, so we have to leave the answer at what we can say for sure. Since it passes 4.5 inches, we know for sure that it is at least 4.5 inches, this being as accurate as we can promise from the units we are give.
