PLATO answer keys are available online through the teacher resources account portion of PLATO. In addition to online answer keys, printed PLATO instructor materials also typically have an answer key.
The PLATO answer key is accessible online when the unit test screen is open. Go to View Answer Key in the unit test screen, and either view the answers online or print them off. Occasionally, pop-up blockers make viewing unit tests or answer keys online difficult, so turn them off if necessary. Although PLATO doesn't always provide an answer key to tests requiring subjective answers, it does provide rubrics in teacher guides for grading these answers.