Free material works best as a starting point, not the whole plan. Coverage tends to skew toward whatever topics were easiest to write questions for, and explanations are often thin — a bare right-or-wrong without much reasoning behind it. That's fine for confirming what you already know, but it won't teach you much on a topic you're genuinely unsure about.

Use free questions to find your weak spots, then dig deeper into the specific areas that need work rather than treating a good score as proof you're ready. Multi-response questions especially deserve careful review, since the real exam gives no credit for partially correct answers. Free resources get you oriented fast — just don't stop there if you're serious about passing.