The basic elements of public-opinion research are interviewers, questionnaires

21/50

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

The basic elements of public-opinion research are interviewers, questionnaires, tabulating equipment, and to sample population.

basic elements

are

tabulating

and to sample

Giải thích

Đáp án D

To sample → sampling vì hai động từ nối với nhau bằng liên từ and phải cùng dạng để đảm bảo sự hài hòa