A. With the advent of better imaging technologies and space-based telescopes,
the number of planets discovered outside our solar system
have steadily increased.
'THE NUMBER OF' construction requires singular verb form against 'A NUMBER OF' construction which requires plural verb form.B. With the advent of better imaging technologies and space-based telescopes,
the number of planets discovered outside our solar system
has steadily increased
Correct choiceC. Steadily increasing due to the advent of better imaging technologies and spacebased telescopes have been the number of planets discovered outside our solar system.
Awkward construction.D. Better imaging technologies and space-based telescopes have steadily
increased the discovery of planets outside our solar system.
Its the discovered planets not the Discovery, which has increased.E.
The number of planets discovered outside our solar system
are steadily increasing with the advent of better imaging telescopes and space-based telescopes.
same as choice A