If there is an open circuit which of the following could be used to complete the
circuit?
a nickel
a paper cup
a piece of paper. a piece of yarn

The answer is a nickel

Explanation:

Why? Because nickel is a type of iron and electrons are made up of electricity. Iron attracts electricity, while a paper cup, a piece of paper, and a piece of yarn don't.  

straight fertilizers

carbohydrates: (starches and sugars) composed of carbon, hydrogen, and oxygen.

lipids: (fats, oils, and waxes) are made of carbon and hydrogen atoms.

nucleic acids: contain hydrogen, oxygen, nitrogen, carbon, and phosphorus. they are polymers of nucleotides. a nucleotide has three parts, a 5-carbon sugar, a phosphate     (-po⬇️4) group, and a nitrogenous base.

proteins: made up of nitrogen, carbon, hydrogen, and oxygen. they are polymers of amino acids.