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').

Embryos develop and hatch in about four weeks, then spend four to ____ months in the tadpole stage.\Question: Choose the right answer from options given a) five b) nine c) eight d) two
a

Verbs have ____ functions in sentences.\Question: Choose the right answer from options given a) two b) eight c) no d) ten
a

Echocardiography demonstrates in clear, graphic fashion the ____ cardiac chambers and four valves.\Question: Choose the right answer from options given a) one b) two c) six d) four
d