When formaldehyde and potassium hydroxide are heated, we get A. Acetylene B. Methyl alcohol C. Methane D. Ethyl formate

The reaction is as follows:

$$\ce{HCHO + KOH -> CH3COOCH2CH3 + H2O}$$

Acetylene (A) is a colorless gas with a garlic-like odor. It is used as a fuel and a chemical intermediate.

Methyl alcohol (B) is a colorless liquid with a strong odor. It is used as a solvent, a fuel, and a chemical intermediate.

Methane (C) is a colorless, odorless gas. It is the simplest alkane and the main component of natural gas.

Ethyl formate (D) is a colorless liquid with a pleasant fruity odor. It is used as a solvent, a flavoring agent, and a fragrance.