Don't play a trick ______ him. [ ]
A. at
B. on
C. to
D. for
答案:B
设集合A={-1,1,3},B={a+2,a2+4},A∩B={1},则实数a=______.
债权人只能向特定的债务人主张权利,这体现的是()。
A.请求权
B.支配权
C.相对权
D.形成权