( )不是钢电弧焊时氢的来源。
A．锈中结晶水
B．焊件和焊丝表面的油污
C．焊条药皮和埋弧焊剂中的水分
D．母材和焊丝中的氢
参考答案：D
A．( The apple is one of the fruits that can lower your blood sugar
B．( Apples are sugar-containing fruits that may raise your blood sugar
C．( Although it is sugar-containing, the apple is a kind of healthy fruits
D．( For those who are on a diet, an apple a day is enough because it digests slowly
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