Answer: Ease and Increase
A. To ease, it means to lower the [difficulty] but increase is basically the opposite.
B. Roam means to wander around or aimlessly walk and stroll is quite similar, meaning to take a walk.
C. An assignment is basically a task, something that should be completed.
D. A riddle is a question that is to be solved, a puzzle being the same, but it doesn’t have to be a question.