Look at the image above that posted in the answer to get an idea of what is 90 degrees and lees than 90 degrees.
Now let us find which angles are less than 90 degrees from you answer options. I will choose one and you will find the rest. If you need help then I will give you hints and help you, but try it yourself too. So the answer I choose is the first top left box. That is one of the ans answers. Now it is your turn.