How many variables should there be in a well-designed experiment?

What effects result when there is an impact between earth and an asteroid? check all that apply. a.massive flooding. b.extinction of many life forms.c.major earthquakes change in average global temperature.d. giant dust cloud

Which additional product balances the reaction h2so4 + 2naoh → na2so4 + 2h2o 2oh h2o2 h3o

Acar travels in reverse. it covers 150 meters in 12 seconds what is the velocity of the car what is the speed of the car