题干

实验小组为探究“乳酸菌无氧呼吸是否有气体产生”,设计如下图所示的两个实验装置,两装置均置于25℃的恒温水浴中,下列说法正确的是

A:乙装置的气球中应注入甲装置等量的乳酸菌培养液并通入O2

B:实验中使用的培养液需煮沸冷却处理,目的是控制自变量

C:25℃恒温的目的只是控制环境温度变化对实验的影响

D:预期最可能的实验结果是两个烧杯液面基本无变化

上一题 下一题 0.0难度 选择题 更新时间:2018-11-16 01:10:25

答案(点此获取答案解析)

D

同类题5

补全短文。根据短文内容,从短文后的A-F选项中,选出5个适当的选项补全短文。

Try to help your dog relax

    It's a Saturday morning. You rush through breakfast, walk the dog, and then get to soccer practice on time. A few hours later, you return home, only to find that the dog has made your bedroom untidy.  ____ Your favorite sports shoes are in poor condition.

    Before you get angry, stop and think. Your dog wasn't misbehaving (行为不端) just for the fun of it. ____ Some dogs just feel nervous when left alone. It's called separation anxiety (分离焦虑).

    Think of it this way: Dogs can't ask where you're going or when you'll be back. They can't call you on the phone. ____ Since you're not there, they need to find you. Dogs may suddenly develop separation anxiety. But with practice and patience (耐心), you can teach your dog to be comfortable being left alone.

    Put on your jacket, and then sit back down. Open and close the door, and then sit down. After a while, walk out the door for 10 seconds, then 20, then a minute and so on. ____

    Besides, you can also try the following ways:

    Teach your dog a word or action that you use every time you leave, which tells your dog you'll be back.

    Help comfort (安慰) your dog by leaving a piece of clothing that smells like you.

    Before you leave, give your dog a toy. ____ 

A. Your clothes are on the floor.

B. It will keep him / her busy while you're away.

C. And he / she wasn't punishing you for leaving.

D. All they know is that they want to be with you.

E. Little by little your dog will learn that when you leave, you will return.

F. You can help your dog by offering him / her some food.