内混式喷枪通常有（）套供气系统。
A.一套
B.两套
C.三套
D.四套
参考答案：B
大肠癌的好发部位依次是（）
A.直肠、乙状结肠、盲肠、升结肠、横结肠、降结肠
B.直肠、升结肠、降结肠、乙状结肠、横结肠、盲肠
C.直肠、乙状结肠、横结肠、升结肠、降结肠、盲肠
D.升结肠、横结肠、盲肠、降结肠、乙状结肠、直肠
E.升结肠、降结肠、盲肠、横结肠、直肠、乙状结肠
He is a person _____ jokes with people.[ ]
A. who enjoys playing
B. enjoys playing
C. who enjoy playing
D. enjoys to play
