The ______ layer starts at Earth's surface and extends 8 to 14.5 km high (5 to 9 miles). This part of the atmosphere is the densest and almost all weather is in this region.

The ______ layer starts at Earth's surface and extends 8 to 14.5 km hi

1.	The ______ layer starts at Earth's surface and extends 8 to 14.5 km high (5 to 9 miles). This part of the atmosphere is the densest and almost all weather is in this region.
A.	Troposphere
B.	Ionosphere
C.	Stratosphere
D.	Mesosphere
Answer» B. Ionosphere