I think the answer is A. not entirely sure
1.), missing links
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Explanation:
Tests for gases
Hydrogen, oxygen, carbon dioxide, ammonia and chlorine can be identified using different tests.
Hydrogen. A lighted wooden splint makes a popping sound in a test tube of hydrogen.
Oxygen. A glowing wooden splint relights in a test tube of oxygen.
Hi,
The answer should be letter B, as H2O is a compound made of two different elements in a definite proportion.