in a scientific experiment, how many independent variables should be tested
at the same time?
o a) none
ob) one
oc) two
od) three or more

The correct option is b) one

Explanation:

An independent variable can be described as a variable which is changed or varied in order to test its effect on the dependent variable. Although multiple variants can be changed at a certain time but it is best to change and see the results of one independent variable at a time. This will allow more valid results to be deduced. Hence, accurate results can be made if one variable is changed at a time.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.