You can't assume anything by the drawings - especially in DS. In that section the drawings can be drawn completely out of scale. In problem solving the drawings are to scale unless it is noted otherwise but even scale can't be use to see a perfect bisection.

Becky is exactly right - you cannot deduce from the drawings except that lines that appear straight are straight and things that are labeled on the drawing are accurate as well, for example the 90 degree angle sign.

The point of the test is to use quantitative reasoning and not to deduce things from the way the drawings are made.

And even if you could rely on the drawings, you are not allowed to bring a ruler into test - I am surprised they still allow you to wear your shoes into the test center with all of the security they have now!