(23x2y-6xy)•(12xy),
=23×12x2+1y2-6×12x2y2,
=13x3y2-3x2y2.
Her sister ______ a rich man. They ______ for twenty years.
A.married with; have married
B.married to; have married
C.married; have been married
D.has married with; have been married
弗洛伊德的心理性欲发展学说认为性欲发展可分为:口欲期、肛欲期、恋母期及生殖器期、潜伏期和()
A.享乐期
B.性器期
C.性欲期
D.生殖期
E.吮吸期