My guess would be choice D
The answer would be, the iris. Hope this helps:)
The answer is B. The electric screw driver increased the work. You would rather have an electric one than doing it all by hand. Hope this helps!
A concave lens can only form a virtual image. The correct option among all the options that are given in the question is the third option or option "C". Concave lenses are mostly thinner in the middle compared to its edges. I hope that this answer has come to your help.
