下面哪个句子适合做主题句? ( )
A: The importance of gold.
B: Three causes of the War of 1812.
C: Driving on freeways requires skill and alertness.
D: American food is tasteless and greedy.
A: The importance of gold.
B: Three causes of the War of 1812.
C: Driving on freeways requires skill and alertness.
D: American food is tasteless and greedy.