判断char型变量ch是否为小写字母的正确表达式是（）。

A.('a'>=ch)||('z'<=ch)

B.'a'<=ch<='z'

C.(ch>=a)&&(ch<=z)

D.(ch>='a')&&(ch<='z')

A.('a'>=ch)||('z'<=ch)

B.'a'<=ch<='z'

C.(ch>=a)&&(ch<=z)

D.(ch>='a')&&(ch<='z')

A.’a’<=ch<=’z’

B.(ch>=’a’)&(ch<=’z’)

C.(ch>=’a’)&&(ch<=’z’)

D.(‘a’<=ch)and(‘z’>=ch)

A.'a'<=ch<='z'

B.(ch>='a') &(ch<='z')

C.(ch>='a') &&(ch<='z')

D.('a'<=ch)AND ('z'>=ch)

A.'a'<=ch<='z'

B.(ch>='a') & (ch<='z')

C.(ch>='a')&& (ch<='z')

D.('a'<=ch) AND ('z'>=ch)

A.'a' <= ch <= 'z'

B.(ch >= a) && (ch <= z)

C.(ch >= 'a') && (ch <= 'z')

D.('a' >= ch) || ('z' <= ch)