List three things that cause the body to begin puberty

Testosterone is the hormone that causes most of the changes in a boy's body during puberty, and men need sperm to be able to reproduce. In girls, the hormone, estrogen, targets the two ovaries, which contain eggs that have been in the girl's body since she was born.  Have a good day :)

Puberty starts when a hormone that releases gonadotropin is secreted, setting off chemical messages, in special inside the hypothalamus. The pituitary gland is stimulated to produce its own messengers: a follicle stimulating hormone, and a lutenizing hormone. The raised levels of these two causes the body to produce sex hormaones, such as testosterone.

by 1890, the united states had by far the world's most productive economy. american industry produced twice as much as its closest competitor--britain. but the united states was not a great military or diplomatic power. its army numbered less than 30,000 troops, and its navy had only about 10,000 seamen. britain's army was five times the size of its american counterpart, and its navy was ten times bigger. the united states' military was small because the country was situated between two large oceans and was surrounded by weak or friendly nations. it faced no serious military threats and had little interest in asserting military power overseas.

the answer is c. to explore the louisiana purchase