"abcdefg"[::-1]的结果是多少?
A."gfedcba"
B."abc"
C."abcde"
D."abcdefg"
a = "abc",则 a * 2的结果是?
A.“abc2”
B.“abc”
C.“abcabc”
D.报错
a = "abc",下列哪个语句可以将a中的字母全部大写?
A.a.replace("a", "A")
B.a = a.replace("a", "A")
C.a.lower()
D.a.upper()
a = “abc”,下列哪个语句可以计算a中字符串"a"出现的次数?
A.a.count(a)
B.a.count('a')
C.a.index('a')
D.a.index(a)