A:however may it cost
B:no matter how much it cost
C:however much it is cost
D:however much it may cost
按拼音写汉字。
yán jiū
gōng kè
lù jìng
cuī cù
____
①气压沉箱法
②“人”字形路线
③直井施工法
④传统打桩法
目前,我国仍然是以煤炭火力发电为主,形成这些煤的植物类群主要是古代的( )