Concept:The atmosphere is arranged in layers, and the lowest layer is the one directly above Earth's surface.
Explanation:From Earth's surface upward, the atmospheric layers follow this order:
Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
The troposphere is the first layer, extending from ground level up to roughly 8 to 16 km.
It contains about 75% of the atmosphere's mass and is where weather phenomena and clouds occur.
Since it is the closest layer to the ground, it is the lowest layer of the atmosphere.
The other options lie above it: the Stratosphere is the second layer, the Thermosphere is the fourth layer, and the Exosphere is the outermost layer.
Therefore, the correct option is the troposphere.
Answer:B. troposphere