1．To travel to the United States，you must first apply________the American Embassy________your visa.
A．for；to B．to；for
C．for；for D．to；to
2．When my neighbours came out to do morning exercises，I also________.
A．joined B．joined in
C．attended D．took part in
3．He began to take political science________only when he left school.
A．strictly B．truly
C．carefully D．seriously
