单选题 test.txt为一个空白txt文件,执行以下代码,结果正确的是:with open("test.txt", "a") as f: f.writelines("明月松间照,清泉石上流.\n竹喧归浣女,莲动下渔舟.\n随意春芳歇,王孙自可留. \n ") with open("test.txt", "r") as f: strings = f.readline() print(strings)