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').

Batteries consist of ____ electrodes immersed in an electrolyte.\Question: Choose the right answer from options given a) two b) eight c) three d) seven
a

Mares abort suddenly without signs of illness, and the fetus shows ____ signs of degenerative change.\Question: Choose the right answer from options given a) zero b) no c) seven d) ten
b

Adult hemoglobin has two alpha and ____ beta chains.\Question: Choose the right answer from options given a) two b) zero c) four d) ten

a