Closed-ended questions are useful because a. They are easily ...

[penguins]

Closed-ended questions are useful because
 
  a. They are easily standardized and coded
  b. Often all the possible responses are not needed
  c. Participants can formulate their own responses
  d. It's easy to anticipate the range of response alternatives for most questions

Question 2

Open-ended questions are more appropriate for
 
  a. preliminary studies
  b. large-scale studies
  c. follow-up studies
  d. studies in which you don't want respondents to have to think too hard

[zhanghao]

Answer to Question 1

a

Answer to Question 2

a

[penguins]

Excellent

[momolu]

Gracias!