In my opinion, the first thing ()is what tools we should use.

单项选择题This is one of the main ways ()a business learns what customers want.

单项选择题Our advertising rates are()size and location.

单项选择题Sometimes it（）over half the total time spent on a research problem.？（）

A.takes up
B.takes off
C.takes on

单项选择题Born into a rich family, he has no idea of () to be a poor man

单项选择题A good hunting dog is () every sound and movement in the field.