What is the IUPAC name and common name for the compound HC riplebond CCH3?

The presence of a carbon-carbon triple bond ($C \equiv C$) indicates that this compound is an alkyne.

The compound has three carbon atoms in a continuous chain: $C-C \equiv C$.

A three-carbon chain is based on "propane". Since it's an alkyne, the suffix changes to "-yne". Thus, the systematic IUPAC name is propyne. For a three-carbon alkyne, the triple bond can only be at the first position, so it's often simply called propyne (or prop-1-yne).

• A) Acetylene: This is the common name for ethyne ($HC \equiv CH$), which has two carbon atoms. This is incorrect.
• B) Methyl acetylene: This is a common name for propyne ($HC \equiv CCH_3$). It can be thought of as an acetylene molecule ($HC \equiv CH$) where one hydrogen atom has been replaced by a methyl group ($CH_3$). This matches the given compound.
• C) Butanol: This is an alcohol with four carbon atoms ($C_4H_9OH$). This is incorrect.
• D) Decanoic acid: This is a carboxylic acid with ten carbon atoms ($CH_3(CH_2)_8COOH$). This is incorrect.

Although the question asks for the IUPAC name and "propyne" is the strict IUPAC name, "methyl acetylene" is a widely accepted common name for propyne and is the only option that correctly identifies the given compound. In multiple-choice questions, if the systematic IUPAC name is not provided, a correct and unambiguous common name is often the intended answer.

The correct option is B.

The final answer is $\boxed{\text{B) Methyl acetylene}}$.