输入一行字符，分别统计出其中英文字母、空格、数字和其它字符的个数。思路：利用while语句，条件为输入的字符s = input('input a string:')letters = 0space = 0digit = 0others = 0for c in s:if c.isalpha():letters += 1elif c.isspace():space += 1elif _________:digit += 1else:others += 1print('char = %d, space = %d,digit = %d,others = %d' % (letters,space,digit,others))

A. c.isDigit()
B. c.isdigit()
C. c.IsDigit()
D. c.Digit()