When did Puerto Rico because a state

It did not become a state, however it did become part of U.S territory.  In 1917, Puerto Rico became a U.S. territory and its people became U.S citizens. So, it became part of the U.S in 1917.

Explanation:

this defines the ability for a flex item to grow if necessary. it accepts a unitless value that serves as a proportion. it dictates what amount of the available space inside the flex container the item should take up.

give brainlest

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain