One-tailed vs. Two-tailed tests

What is a major difference between a one-tailed significance test and a two-tailed significance test?

The two-tailed test uses a test statistic, whereas the one-tailed test uses the critical region.

For a given alpha level, Z(critical) is less extreme for the one-tailed test.

For a given alpha level, Z(critical) is more extreme for the one-tailed test.

The one-tailed test uses a test statistic, whereas the two-tailed test uses the critical region.