Help with a few biology questions.?

1.
Nitrogen gas is an element because it contains only one kind of atoms (nitrogen atoms). Nitrogen gas exists as N≡N molecules.

Sodium chloride (NaCl), fructose (C₆H₁₂O₆) and hydrochloric acid (HCl) are compounds. This is because each of them contains two or more kinds of atoms.

The answer: C. Nitrogen gas

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2.
I think this question is in the field of biochemistry.
Refer to: https://en.wikipedia.org/wiki/Mineral_(nutrient)
The trace elements that have a specific biochemical function in the human body are sulfur, iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine and selenium.

The answer: C. sulfur

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3.
The more reactive the metal, the less electronegative the metal is.
Among the 4 options, rubidium is the most reactive metal, and thus rubidium has the least electronegative.

The answer: B. Rubidium

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4.
Entropy is a measure of disorder.
Entropy is part of the 2nd law of thermodynamics, while enthalpy is part of the 1st law.

The answer: B and C

C. Nitrogen gas

2. A. Silicon

3. B. Rubidium

4. E. B and C