从词的构造方式看，下列各项中属于复合词的是

A、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">木头</span>

B、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">念头</span>

C、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">苦头</span>

D、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">山头</span>