题干

把一个细胞中的磷脂分子全部提取出来,在空气和水界面上将它们铺成单分子层(假定单分子间距离适当且相等),推测在下列生物中,空气和水界面上磷脂分子层的表面积与原细胞的表面积之比最大和最小的细胞分别是()

①洋葱根尖成熟区表皮细胞②蛙的红细胞③唾液腺细胞④乳酸菌细胞⑤酵母菌细胞.

A:①②

B:③④

C:③②

D:⑤④

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答案(点此获取答案解析)

B

同类题5

阅读下列短文,从每篇短文后各题所给的四个选项(A、B、C和D)中,选出最佳选项。

     “I see you've got a bit of water on your coat,” said the man at the petrol station. “Is it raining out there?”“No, it's pretty nice,” I replied, checking my sleeve. “Oh, right. A pony(马驹) bit me earlier.”

As it happened, the bite was virtually painless: more the kind of small bite you might get from a naughty child. The pony responsible was queuing up for some ice cream in the car park near Haytor, and perhaps thought I'd jumped in ahead of him.

    The reason why the ponies here are naughty is that Haytor is a tourist-heavy area and tourists are constantly feeding the ponies foods, despite sighs asking them not to. By feeding the ponies, tourists increase the risk of them getting hit by a car, and make them harder to gather during the area's annual pony drift(迁移).

    The purpose of a pony drift is to gather them up so their health can be checked, the baby ones can be stooped from feeding on their mother's milk, and those who've gone beyond their limited area can be returned to their correct area. Some of them are also later sold, in order to limit the number of ponies according to the rules set by Natural England.

    Three weeks ago, I witnessed a small near-disaster a few mils west of here. While walking, I noticed a pony roll over on his back. “Hello!” I said to him, assuming he was just rolling for fun, but he was very still and, as I got closer, I saw him kicking his legs in the air and breathing heavily. I began to properly worry about him. Fortunately, I managed to get in touch with a Dartmoor's Livestock Protection officer and send her a photo. The officer immediately sent a local farmer out to check on the pony. The pony had actually been trapped between two rocks. The farmer freed him, and he began to run happily around again.

    Dartmoor has 1,000 or so ponies, who play a critical role in creating the diversity of species in this area. Many people are working hard to preserve these ponies, and trying to come up with plans to find a sustainable(可持续的) future for one of Dartmoor's most financially-troubled elements.