Which form of birth control could people use without altering hormonal systems or blocking sperm from fertilizing an egg? fertility awareness birth control pills condom

The answer would be Fertility Awareness.

Fertility Awareness is basically making a calendar that measures one's ovulation periods to designate "safe days" where one cannot get pregnant.

Birth control pills alter hormonal systems by giving women two hormones called estrogen and progestin to prevent pregnancy.

Condoms simply block the sperm from getting to the egg to prevent or lower chances of becoming pregnant.