34) A

Newborn baby
Mass of breast milk consumed = 560 g
Mass of protein consumed = 2.5% of 560 = 14 g (info from 3rd paragraph 1st line)
For each gram of protein, 55 mg of isoleucine is consumed.
Mass of isoleucine consumed = 55 x 14 = 770 mg

8-week old baby
Mass of breast milk consumed = 700 g
Mass of protein consumed = 1% of 700 = 7 g
For each gram of protein, 55 mg of isoleucine is consumed.
Mass of isoleucine consumed = 55 x 7 = 385 mg

Ratio = 770 : 385 = 2 : 1