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').

Electrons have almost ____ mass and are negatively charged.\Question: Choose the right answer from options given a) three b) seven c) zero d) no
d

Vaccinated newborns have protection for at least ____ years.\Question: Choose the right answer from options given a) four b) five c) two d) no
b

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

a