土壤呈酸性不利于农作物的生长，我们可以将适量的______加入土壤，进行改良．

How many people are directors of both Company K and Company R ？（）
(1)There were 17 directors present at a joint meeting of the directors of Company K and Company R, and no directors were absent,
(2)Company K has 12 directors and Company R has 8 directors.

A.条件（1）充分，但条件（2）不充分.

B.条件（2）充分，但条件（1）不充分.

C.条件（1）和（2）单独都不充分，但条件（1）和条件（2）联合起来充分.

D.条件（1）充分，条件（2）也充分.

E.条件（1）和条件（2）单独都不充分，条件（1）和条件（2）联合起来也不充分.