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').

Blood pressure is measured by ____ numbers.\Question: Choose the right answer from options given a) zero b) eight c) two d) seven
c

Natural chlorine contains ____ isotopes.\Question: Choose the right answer from options given a) two b) six c) eight d) seven
a

Nucleosides can combine with one, two or ____ phosphates .\Question: Choose the right answer from options given a) seven b) three c) five d) four

b