_____ is one of the principal gases contributing to the greenhouse effect. A: Formaldehyde B: Methane C: Benzene D: Nitrogen
_____ is one of the principal gases contributing to the greenhouse effect. A: Formaldehyde B: Methane C: Benzene D: Nitrogen
在下列塑料中,属于热固性塑料的是(<br/>)塑料。 A: PVC B: PE C: phenol<br/>formaldehyde D: PP
在下列塑料中,属于热固性塑料的是(<br/>)塑料。 A: PVC B: PE C: phenol<br/>formaldehyde D: PP
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