Which sentence contains gender-neutral language?
the firemen loaded their equipment and started up the ladder.
the stewardess load passengers onto the plane.
a company is looking to replace the chairman of the board.
recycling preserve the earth for all humankind.

The answer to the given question above would be the last option. The sentence that contains gender-neutral language is the following one: Recycling helps preserve the Earth for all humankind.

Humankind is an abstract noun which refers to all the humans in the world: children, women and men. On the contrary, sentence A, "the firemen loaded (...)" makes use of the noun "firemen" which takes "men" as a suffix and it only refers to the men.  "Steardness" refers to women who take care of passengers in either a shift or an aircraft. Finally, the last sentence takes "chairman", so the same reasons as in the first sentence apply.

D. Recycling helps preserve the Earth for all humankind

Explanation:

jefferson introduced the idea that one does not change a government for "light" causes because he wanted to emphasize the seriousness of colonists' reasons for declaring independence.

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