What is the magnetosphere?

the region surrounding the earth or another astronomical body in which its magnetic field is the predominant effective magnetic field. the region of Earth's magnetic field shaped by the solar wind

Explanation:

A magnetosphere is a region around any celestial body producing magnetic field. It is the portion of magnetic field around the Earth which interacts with the charged particles emitting from the sun at high speeds. It is a pear shaped magnetic field region surrounding the Earth. It is shaped by the solar wind.

Thus, the correct answer is b. the region of Earth's magnetic field shaped by the solar wind