题目

 I ________ on a sofa because my grandparents have been here for the weekend. A. sleeps                    B. was sleeping     C. have slept        D. am sleeping 答案：D有一条多肽链，分子式为CxHyOpNqS，将它彻底水解后，只得到下列四种氨基酸．分析推算可知，水解得到的氨基酸个数为（　　） A、q+1B、p+1C、q-2D、p-1