声波探测法检测混凝土强度时，声波频率越低，传播距离越小。
参考答案：错
皮碗清洁器由橡胶皮碗、压板法兰、导向器、发讯器以及护罩等组成，使用时要确保（）灵敏可靠。
A.发讯器
B.压板法兰
C.导向器
D.刚性骨架
Directions:
The graphs below show the types of music albums purchased by people in Britain according to sex and age.
Write a report for a university lecturer describing the information shown below. You should write about 160-200 words neatly on ANSWER SHEET2.
