下列叙述与图中的实验装置相符合的是（　　）

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. ____ 

在各项都为正数的等比数列$\left\{a_n\right\}$中，首项为3，前3项和为21，则$a_3$等于（   ）

图甲为豌豆的一对相对性状遗传实验过程图解；图乙是果蝇的精原细胞分裂产生精子细胞的示意图．请仔细读图后回答下列问题：

（1）甲图实验的亲本中，母本是____ ；为了确保杂交实验成功，①的操作应注意____，时间应该在____ ．

（2）甲图实验中，操作②叫____ ，此处理后必需用纸袋对母本进行套袋隔离，其目的是____ ．

（3）乙图Ⅱ细胞的名称是____ ，每个细胞中有____ 条染色体．图Ⅲ每个细胞的核DNA含量是①阶段细胞的　____ 　．

（4）减数分裂中染色体数目减半的根本原因是____．

如图所示，如果想考察该历史遗址，应该去的国家是