A certain alloy contains only lead, copper, and tin. How many pounds of tin are contained in 56 pounds of the alloy ?()
(1)By weight the alloy is lead and
copper.
(2)By weight the alloy contains 6 parts lead and 5 parts copper
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.
参考答案:A
解析:
本题的正确答案为(A) 。由(1)中的铅在该合金中所占的比例等于[*],铜的比例等于[*]可推知锡所占的比例等于[*],用锡的总量56乘以所占的比例[*]可以得到锡的量,所以(1)单独能充分回答上面的问题;因根据条件(2)无法判断共有多少parts,所以其单独无法充分回答上面的问题。