[求助]涛涛GWD6

forgetviviva

26 

K is a set of integers such that if the integer r is in K, then r + 1 is also in K.  Is 100 in K?

(1)     50 is in K.

(2)     150 is in K.

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案是A,不知道是怎么算 出来的？？谢谢帮忙

forgetviviva

 谢谢，说得很明白!!!

wujie_rens

if 50 is in K, then 50+1 is in K, then 51+1 is in K, then ... then 99+1 is in K

but if 150 is in K, we can not assure that 100 is in K, maybe the minimum in K is greater than 100