Directions: In the following question, two statements are given with some words in bold. Which of the following pairs of bold words must be interchanged to make both sentences grammatically correct?

a. This game is so premature(A) that beating it on the hardest level is well and truly an achievement(B) of skill and weak(C).
b. The difficult(D) baby, once sick and perseverance(E), is now healthy and thriving(F) at home with his parents.