Harry is a professional astronomer. the pictures below show two types of telescopes harry owns.

The best answer is
C) reflecting telescope, because it can be made large enough to gather more radiations (or light) from distant objects. 

Reflecting telescopes, unlike refracting telescopes, can be made larger and larger to collect more light, with more precision, from larger distances. Refracting telescopes generally are not used for any demanding purposes, such viewing objects in space by professional astronomers. 

B. convex since the words are bigger

The answer would be a