is not a reducing agent; peroxides (compounds with the formula R-O-O-R) are oxidizing agents. A very common peroxide is sodium peroxide .

All of the other listed compounds are reducing agents.

produces a trans-alkene from an alkyne whereas produces a cis-alkene. reduces an alkyne all the way down to an alkane. is a strong oxidizing agent.

This is a standard organolithium reaction.

The organolithium product can be thought of as a strong nucleophile. The carbon steals an electron from the lithium to create . From there, the highly reactive carbo-anion is free to attack the ketone at the site of its carbon to form a tertiary alcohol on the cyclohexane.

is the only answer choice that is not an oxidizing agent. In fact, it is a reducing agent because of the lack of oxygen atoms present. This compound adds hydrogen atoms to a compound, thereby reducing it.

Alkenes can be reduced in the presence of and a metal catalyst like platinum to hydrogenate the alkene to give a saturated alkane. The reaction occurs in a heterogeneous solution rather than a homogenous solution. It occurs on the presence of a solid surface of the metal catalyst.

Note that the three carbon-carbon double bonds in the aromatic ring in the presence of the reducing agent does not get reduced because they are extremely stable due to resonance.