下面哪个程序是语法正确的？ A: foo::IO() foo=do line=getLine printline B: foo::IO() foo=do letline=getLine printline C: foo::IO() foo=do letline-getLine printline D: foo::IO() foo=do line-getLine printline

下面哪个程序是语法正确的？ A: foo::IO() foo=do line-getLine n=readline::Int printn B: foo::IO() foo=do line-getLine n-readline::Int printn C: foo::IO() foo=do line-getLine letn=readline::Int printn D: foo::IO() foo=do letline=getLine letn=readline::Int printn