Given a sentence with a missing word, pick the answer option that best fills out the missing word in the sentence. Indicate each answer with its index ('a', 'b', 'c', 'd').

Bacteria come in ____ basic shapes.\Question: Choose the right answer from options given a) five b) one c) three d) nine
c

Astronauts sleep only ____ hours each night, on average.\Question: Choose the right answer from options given a) six b) one c) four d) seven
a

Reptiles often possess at least ____ pigments.\Question: Choose the right answer from options given a) two b) six c) four d) five

a