How many variables should be tested at one time in a scientific investigation?

The varibles are independent varible and dependent varible

The two main variables are:

Independent variable.
Dependent variable.

The issue of racism greatly inflience herbecause by then there was racio discrimination in the south this affects her such that she will grow up favouring people of her race and undermining the othersracism will build herin earlier days the people of south were oppressed by the whites since they were considered slaves or subject yo the whites.so as a result of this the whites children grew up bearing in mind that they were more superpower than the black