There were two           students in the class buildings during the earthquake, but          of them failed to run out.

    You might want to think twice before purchasing____(conventional) grown strawberries or spinach(菠菜). According to a new report from the Environmental Working Group(EWG), these foods are the most likely____(pollute) with the pesticide.

    Even low levels of pesticide exposure can be harmful to infants, babies and young children,____parents and caregivers should take measures to lower children's exposures____pesticides while still____(feed) them diets rich in healthy fruits and vegetables.

    Just last year, the red berry knocked apples and____(hold) the title of the most polluted. The pesticide increased in strawberries because of out-of-season demand. The most polluted strawberry had traces of 20____(vary) pesticides.

    Also moving up on____list this year is spinach. Spinach jumps from the____(eight) to the second most polluted product. The study finds spinach samples contain more pesticides by weight than all other produce____(test). In high doses, it can cause damage to the nervous system.

细胞的分化、衰老和凋亡是普遍存在的生命现象，下列有关叙述正确的是（　　）