密接式钩缓装置需要与普通自动车钩连挂时,必须采用()
参考答案:过渡车钩
—Do you make these flowers _____?
—Oh, no, in fact, they are made by machine. [ ]
A. by hand
B. by your hands
C. with hand
D. with hands
下列有关小肠的结构特点与其吸收功能相适应的是( )
①绒毛壁只由一层上皮细胞组成 ②小肠内表面有许多小肠绒毛
③小肠绒毛内有毛细血管和毛细淋巴管 ④肠腺是粘膜上皮凹陷而成.
A.①④
B.①②③
C.②④
D.②③④