题目

函数f（x）=sin2x+3cos2x的最小正周期是(    ) A.               B.                C．π               D．2π 答案：C  解析：本题考查三角函数的化简及周期的求解；据题意知f(x)=1+2cos2x=1+2·=2+cos2x故其周期为π．He            a glass of milk just now. He was very careless. [     ]A. knocked at B. knocked on C. knocked out D. knocked off