Which would be considered common knowledge?
a. the cost of the space program
b. the theories of space scientists
c. the lyrics to a song
d. the names of planets

The correct answer is D.The names of the planets

Explanation:

The term "common knowledge" refers to basic knowledge or information everyone or almost everyone in a society should know, which is usually related to different  subjects and can be universal such as knowing the names of the continents or the name of the planets or specific to a society for example in the U.S. it is considered the number of states is of common knowledge. Additionally, this type of knowledge is broadly accepted by the members of a society or universally accepted and derives from facts or evidence.

Therefore, the statement that would be considered common knowledge is "The names of the planets", because this is basic knowledge and also it is widely accepted and known by almost everyone around the world, which are the main features of common knowledge.

the answer is b. the tomb is underground and dark, and its opening is covered by a heavy grate.