阅读下列短文，从每小题的三个选项中选出最佳选项。 ​
   In North America，most students go to school by bus.The subway is also widely（广泛地） used in some cities.In small towns and cities，many students walk for a long time to school.
   You can see the yellow school bus all over North America.It is a convenient（方便的） way to go to school.Students on the school bus can also chat with their friends.But the bus is slow and does not always pick up the students on time（准时）.
   The subway is very fast.But it is expensive and crowded.And the stops are not close to the school.So students have to walk for a long time after they get off the subway.
   Walking is green and healthy for those who live near school.It's free and it can help students keep fit.However，it is not easy for students to walk with heavy schoolbags.It's also unpleasant if the weather is too hot or cold.
（1）Most students go to school

B

B

in North America.
A.by subway
B.by bus
C.by bike
（2）You can see the

A

A

all over North America.
A.yellow school bus
B.subway
C.yellow taxi
（3）It's very

B

B

if the students go to school by subway in North America.
A.slow
B.expensive
C.convenient
（4）

C

C

to school is green and healthy.
A.Driving
B.Flying
C.Walking