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').
--------
Question: Copper is ____ times higher in dog liver than in human liver.\Question: Choose the right answer from options given a) three b) ten c) six d) one

Answer: b


Question: Photosynthesis occurs in ____ phases.\Question: Choose the right answer from options given a) four b) two c) nine d) five

Answer: b


Question: New species are believed to arrive in the Mediterranean at the rate of ____ to five annually.\Question: Choose the right answer from options given a) seven b) no c) ten d) four

Answer:
d