This is the first time that your parents have been abroad, ______?

    My new Chinese teacher is Miss White. She is funny and kind. Her favourite food is salad because it is fresh and healthy. She can sing English songs and play the guitar. There is a lake in front of her house. Behind the house, there is a mountain. So she often climbs the mountain and plays some sports on the weekend. I like my Chinese teacher.

    Do you know George? He is a little monkey. He lives in a deep forest. He likes jumping and climbing trees. He is happy every day. But he has a shortcoming（缺点）. He is curious（好奇的）.

    One day an old man went by the forest. He cared a lot of hats. George saw the old man, and the old man saw George, too. The old man said to himself, what a lovely monkey! I will catch him. I will take him home.

    The old man sat down and thought over. George saw and also sat down. The old man had an idea. He put a hat on his head, and put other has on the ground, Then be pretended(假装)to sleep.

    George was curious and looked at the hats. "I will be nice if I put a hat on my head, "George thought. Then be climbed down from the tree, picked up a hat and put it on. The hat was too big, and covered George's eyes. George couldn't see. And the old man got up at once and caught him quickly.

Poor George!

甲、乙两位同学分别设计了下述两个实验方案，并都认为如果观察到的现象和自己设计的方案一致，那么即可证明溶液中含有SO₄^2-。

甲同学的方案：溶液白色沉淀沉淀不溶解

乙同学的方案：溶液无沉淀白色沉淀

请评价上述两个方案是否严密，并分别说明理由：