Using some()fuels ,such as natural gas, in vehicles can generally;reduce harmful pollutants and exhaust emissions.
A.optional
B.alternative
C.replacement
D.substitute
正確答案:substitute
Using some()fuels ,such as natural gas, in vehicles can generally;reduce harmful pollutants and exhaust emissions.
A.optional
B.alternative
C.replacement
D.substitute
正確答案:substitute