Answer:
(Z)-4-methyl-2-pentene
Explanation:
Hydrogenation is a syn addition. This implies that the hydrogen atoms add to the same face of the multiple bond.
Hence, if we have the alkyne, 4-methyl-2-pentyne which reacts with excess hydrogen in the presence of a platinum catalyst, we obtain (Z)-4-methyl-2-pentene since the hydrogen atoms add on the same side of the multiple bond.