The correct answer is (a). Jet stream is a fast-flowing, narrow air current found in the upper atmosphere. It is not a factor in the origin of monsoons.
Monsoons are seasonal wind patterns that occur in many parts of the world. They are caused by differences in temperature between the land and the ocean. In the summer, the land heats up faster than the ocean, causing the air to rise. This creates an area of low pressure over the land. The air from the ocean, which is cooler and at higher pressure, then flows in to fill this low pressure area. This is the monsoon wind.
The jet stream is a band of strong winds that flows from west to east in the upper atmosphere. It is located at an altitude of about 10-12 kilometers. The jet stream is not a factor in the origin of monsoons because it is located too high in the atmosphere.
The other options, (b), (c), and (d), are all factors that affect the origin of monsoons.
(b) El Niño is a climate pattern that occurs in the Pacific Ocean every few years. It is characterized by warmer-than-average sea surface temperatures in the eastern Pacific Ocean. El Niño can affect the monsoons by causing changes in the amount of rainfall that falls in different parts of the world.
(c) Temperature variation is another factor that affects the origin of monsoons. The temperature difference between the land and the ocean is what drives the monsoon winds. If the temperature difference is large, the monsoon winds will be stronger.
(d) Western disturbance is a type of weather system that occurs in the Indian subcontinent. It is characterized by a low-pressure system that brings moisture from the Arabian Sea. Western disturbances can affect the monsoons by causing changes in the amount of rainfall that falls in different parts of India.