Question

6 what is the main idea of the text?
a scientists have a very difficult time viewing natural satellites like moons,
planets, and stars because clouds, dust and molecules in the atmosphere
block the view from ground level.
b before the invention of artificial satellites, television signals only went in a
straight line rather than following earth’s curve and were often blocked by
mountains or tall buildings.
c once rockets launch artificial satellites into space, these satellites begin to
orbit earth at different speeds, different heights, and different paths, all
balanced by the pull of earth’s gravity.
d man - made satellites are machines that come in all shapes and sizes for
different purposes, including collecting data and images about earth and
space, and creating better communication systems.

Explanation:

Option A focuses on the difficulty of viewing natural satellites, which is not the main idea. Option B is about television signals before artificial satellites, which is too narrow. Option C is about how artificial satellites orbit, which is a detail. Option D comprehensively covers the nature (machines in various shapes and sizes) and purposes (data collection, communication) of man - made satellites, which is a broad and main - idea - like statement.

Answer:

D. Man - made satellites are machines that come in all shapes and sizes for different purposes, including collecting data and images about Earth and space, and creating better communication systems.