蝗虫的发育要经历卵、若虫、成虫三个时期，若虫与成虫的区别主要表现在（ ）
A．若虫身体较小，生殖器官没有成熟
B．若虫身体较小，无翅，无外骨骼
C．若虫身体较小，生殖器官发育成熟
D．若虫身体较小，有翅，无外骨骼
蝗虫的发育经历卵、若虫、成虫三个时期，属于不完全变态发育，幼虫和成虫的形态结构、生活习性相似，只是大小、翅膀有无、生殖器官等发育程度不同，若虫身体较小，没有翅膀，不会飞，生殖器官没有成熟等．
故选：A．
Passage Four
| It’s so difficult to follow the ups and downs of a 2-year-old．One moment he’s beaming and friendly; the next he’s sullen (愠怒的) and weepy, often for no apparent reason. These mood swings, however, are just part of growing up. They are signs of the emotional changes taking place as your child struggles to take control of actions, impulses, feelings and his body. At this age, your child wants to explore the world and seek adventure. As a result, he’ll spend most of his time testing limits, his own, yours and his environment’s. Unfortunately, he still lacks many of the skills required for the safe accomplishment of everything he needs to do, and he often will need you to protect him. When he oversteps a limit and is pulled back, he often reacts with anger and frustration, possibly with a temper tantrum (发脾气) or sullen rage. He may even strike back by hitting, biting or kicking. At this age, he doesn’t have much control over his emotional impulses, so his anger and frustration tend to erupt suddenly in the form of crying, hitting or screaming. It’s his only way of dealing with the difficult realities of life. He may even act out in ways that unintentionally harm himself or others. It’s all part of being 2. It’s not uncommon for toddlers to be angels when you’re not around, because they don’t trust other people enough to test their limits. But with you, your toddler will be willing to try things that may be dangerous or difficult, because he knows you’ll rescue him if he gets into trouble. Whatever protest pattern he has developed around the end of his first year will probably persist for some time. For instance, when you’re about to leave him with a sitter, he may become angry and throw a tantrum in anticipation of the separation. Or he may whimper, or whine and cling to you. or he could simply become subdued and silent. Whatever his behavior, try not to overreact by scolding or punishing him. The best tactic is to reassure him before you leave that you will be back and, when you return, to praise him for being so patient while you were gone. Take solace in the fact that separations should be much easier by the time he’s 3 years old. |
When a mother is about to separate with her baby, she’d better______.
A．leave without the baby’s knowledge
B．make the baby subdued and silent
C．comfort the baby that she’ll be back soon
D．ignore the baby’s reactions