铝合金的强度较纯铝显著提高，但一般仍保持比重小、耐腐蚀、导热好等特点。
参考答案：对
肾盂癌为（）
A.移行细胞癌
B.透明细胞癌
C.精原细胞肿瘤
D.腺癌
E.鳞癌
A．It makes them noisier than they were 20 years ago.
B．It makes it difficult for them to fall asleep.
C．It affects their work during the day.
D．It does harm to their hearing.
