Many scientists believe that global warming，if ________ ，will cause extreme climate changes this century.
A. not stopping B. not stop
C. not stopped D. without stop
Many scientists believe that global warming，if ________ ，will cause extreme climate changes this century.
A. not stopping B. not stop
C. not stopped D. without stop
C
考查状语从句的省略。if后省略了主语及动词be。