手工焊接用的焊料为（），中间夹松香焊剂。
A、锡镁合金
B、锡铅合金
C、锡合金
D、铅合金
参考答案：B
It is important to have your eyes examined regularly to check for any sign of eye disease that may not
have any ________. [ ]
A. symptom
B. similarity
C. sample
D. shadow
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