Introduction:
Zaid crops are crops that are grown in the summer season, specifically during the months of March to June. These crops have a short duration from sowing to harvesting and are well-suited to regions with high temperatures. They are also known as summer or cash crops.

Explanation:
Out of the given options, the Zaid crop is Pumpkin.

Reasoning:
Let's analyze each option to understand why Pumpkin is the correct answer:

a) Moong:
Moong is a pulse crop and is typically grown during the Kharif season, which is the rainy season between June and September. It requires a longer duration to grow and is not suitable for the Zaid season.

b) Mustard:
Mustard is an oilseed crop and is primarily grown during the Rabi season, which occurs between October and March. It requires cooler temperatures and is not suitable for the Zaid season.

c) Urad:
Urad is a pulse crop that is also grown during the Kharif season. It requires a longer duration to grow and is not suitable for the Zaid season.

d) Pumpkin:
Pumpkin is a vegetable crop that is well-suited for the Zaid season. It has a short duration from sowing to harvesting, typically around 3-4 months. Pumpkin plants thrive in hot temperatures and can tolerate dry conditions, making them ideal for the summer season.

Therefore, the correct answer is Pumpkin as it is the only crop out of the given options that is suitable for cultivation during the Zaid season.

Conclusion:
Zaid crops are grown during the summer season and have a short duration from sowing to harvesting. Out of the given options, Pumpkin is the only crop that fits these criteria. It is important to understand the specific requirements and characteristics of different crops to make informed decisions about their cultivation.