Which books are best to practice MCQs?

I have practiced pyqs and my modules but i think am still lacking in practicing because in my mock tests i do silly mistakes. not that I dont know the concept or the answer but when I recheck my paper, I could solve them. so I think am still lacking practice. Not only for bio but phy, chem too. Can the topper or anybody of you suggest good books or apps (which is free) for just practicing qs??