草履虫的结构中直接与水接触的是（ ）
A．细胞壁
B．表膜
C．细胞质
D．荚膜
草履虫各部分的结构及功能如下图
由上图可知，草履虫是单细胞的动物，无细胞壁；草履虫的表膜相当于细胞膜，直接与水接触，水中溶解的氧气透过表膜进入细胞的内部，细胞内产生的二氧化碳等废物透过表膜排出；细胞质在表膜以内，不直接与水接触；草履虫无荚膜．可见B符合题意．
故选：B
| Reading comprehension. | |
| ( )1. The Hollywood film star Julia Roberts gave birth to twins on Sunday morning at a Southern California hospital, an English reporter said on Sunday. ( )2. Hong Kong actress and singer Kelly Chen for the first time serves as the Brand speaker for 3D-Gold Jewelry. The ad. Telefilm is on show at the night of Dec. 1st, 2006. ( )3. The Museum of Modern Art has opened its doors to the public once again after a ＄425m revamp (翻新). Thousands of people queued up outside the gallery to take a discount entry on its first day. ( )4. Chinese film star Zhang Ziyi will launch her lastest movie Purple Butterfly in America. Zhang Ziyi is one of the most successful Chinese actors this year with her martial-arts epic House of Flying Daggers premiering in the US tomorrow (on Friday). ( )5. Chinese mainland A-list director Chen Kaige's new film The Promise Film Festivals, and even the 2006 Oscars. | |
Choose the best topic from A to F according to the passage.
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