Which statement describes a second-growth forest? 

A)  an uncut stand of trees or a stand that has not been seriously disturbed by humans 
B)  a stand of trees resulting from secondary ecological succession 
C)  a managed tract with uniformly aged trees 
D)  a storehouse of biodiversity

What is the most important way to save energy and money in transportation? 

A)  increase the fuel efficiency of motor vehicles 
B)  switch to hydrogen-powered cars 
C)  switch to electric engines 
D)  ban cars in cities