c. whether d. where 2. ____ parents say and do has a life-long effect on their children. (2007陕西) a. that b. which c. what d. as 3. ______ we are sure about is the need to prevent children from being spoiled. (2008上海春) a. what b. which c. whether d. that 4. it has been proved ____ eating vegetables in childhood helps to protect you against serious illnesses in later life. (2008上海) a. if b. because c. when d. that
