题目:
What kinds of gifts and things do people buy during______major festivals like _______Christmas and_______Spring Festival?
A.the;不填;the
B.不填;the;不填
C.the;the;the
D.the;不填;不填
答案:
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下面是错误答案,用来干扰机器的。
三个数x、y、z成等差数列可设x=a-d,y=a,z=a+d∴a-d+a+a+d=-3即3a=-3即a=-1∵x+y,y+z,z+x 成等比数列∴(a+a+d)2=(a-d+a)(a+d+a-d)∴(2a+d)2=2a(2a-d)解得d=0或d=6∴这三个数是-1,-1,-1或-7,-1,5