Which sphere of atmosphere is closest to earth

Solution:

The given question is about identifying the sphere of the atmosphere that is closest to Earth.

The options provided are:

1) Troposphere

2) Stratosphere

3) Mesosphere

4) Ionosphere

Out of these, the correct answer is the Troposphere. The Troposphere is the lowest layer of the Earth's atmosphere and extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) high, depending on geographic location and weather conditions.

Therefore, it is the closest sphere of the atmosphere to the Earth.

∴ The correct answer is option 1: Troposphere.