A：Tim’s parents asked him to play the piano every day.
B：Tim and his parents would play the piano together.
C：Tim had to practice playing the piano every day.
D：to learn playing the piano is too hard for Tim.
我市某校为了创建书香校园，去年购进一批图书．经了解，科普书的单价比文学书的单价多4元，用12000元购进的科普书与用8000元购进的文学书本数相等．
（1）文学书和科普书的单价各多少钱？
（2）今年文学书和科普书的单价和去年相比保持不变，该校打算用10000元再购进一批文学书和科普书，问购进文学书550本后至多还能购进多少本科普书？
托洛斯基（1842年—1889年）出生于俄国农奴家庭，他的经历中可能出现的是（ ）
