A.Upwardforceanddownwardforceareequal.
C.Downwardforceisgreater.
D.Theearth’spullisnotgreat.
C.Thewaterwilldonothingtoit.
A.Alcoholhelpsdeveloppeople’sintelligence.
B.Heavydrinkingisnotnecessarilyharmfultoone’shealth.
C.Controlleddrinkinghelpspeoplekeeptheirwitsastheyage.
D.Drinking,evenmoderately,mayharmone’shealth.
A.Tolearnwhyhumanpopulationgrowssofast.
B.Tofindouttowhatextentmanisaffectedbylivingspace.
C.Tolearninwhatwayratsarelikehumanbeings.
D.Tofindouthowratsliveanddie.
C.Theytendtoreproducemore.
D.Theytendtobiteeachother.
A.Populationexplosionisinevitable.
B.Overcrowdednesscanhavethesameeffectonman.
C.Foodandspaceareessentialtoallanimals.
D.Populationexplosioncanleadtoviolence.