Since electric and gasoline-electric hybrid cars are currently more expensive than traditional gasoline-powered vehicles, politicians have tried to incentivize the purchase of alternative-fuel cars by .

giving tax break to consumers who buy them

Explanation:

Giving tax break or tax cut is a measure that reduces the amount of money a citizen pay to the government as tax for a particular item or commodity. Tax cut are meant to boost economy, encourage usage or patronage of a particular item.

In this case, a tax break is given as incentive to encourage patronage of alternative-fuel cars despite its expensive cost

giving tax break to consumers who buy them

Explanation:

a.   mass number from atomic number

this could be newton#'s law of cooling. the cooling curve is exponential