I'm so confused by this can someone help me?

I'm so confused by this can someone help me?

Problem 1:

You have information on one sample and want to compare it to the population to see if it is significantly different from the population mean.  In each of the following situations, would it be appropriate to use the t-test OR the z-test?  

1. You know the population mean and variance
2. You do not know the population mean and variance