It is difficult (for) many students (to) (learn) English.
对许多学生来说,学英语很困难.
句型It's + 形容词+ for sb +to do.对某人来说,做某事如何.那是用这句；To many students,English is difficulf to stcdy.改为这一句又怎么改呢；It is difficult () many students ()()English.改为：It's difficult ( for ) many students ( to ) ( study ) English.