The answer is; A
The bright light from the stats they orbit makes its difficult for the exoplanets to be viewed by a telescope because the planets are much dimmer than the stars. Unique telescopes (The Transiting Exoplanet Survey Satellite (TESS) & Kepler telescope) are able to search for these exoplanets by utilizing the phenomenon where the stars tend to dim after regular intervals of time hence signifying a planet orbiting the star. Depending on the dimming, the size of the planet can also be deduced.
