which one out of the following is dependent variable  of the given equation:
X= 1- t²

The correct answer is: x

The given equation x = 1 - t²
Dependent variable means a variable that changes the value with the another variable.
Independent variable doesn’t change value according to the equation.
In the above equation the value of x changes with t. So, x is the dependent variable.

For such questions, the isolated variable is considered dependant variable.