I'm Lucy. There are four people in my family. They are my grandfather, my parents and me. My grandfather likes to plant flowers. He works on his farm every morning. My father likes to watch TV. He likes to watch the news very much. My mother likes to go shopping. She often buys new clothes for us. I like to read books. I go to the library on Sundays.

从经济的角度看，明清时期中国已处于“近代的前夜”。下列史实最能说明这结论的是（    ）

在以下人体细胞中，能或可能找到两个X染色体的是
①精原细胞      ②卵原细胞      ③初级精母细胞
④初级卵母细胞  ⑤次级精母细胞  ⑥次级卵母细胞

下列曲线表示减数分裂过程中DNA含量变化的是（　　）