I am really weak in multiple choice how do I improve?
Since I'm guessing you're talking about in the context of Prelims and the HSC since we don't have to do IQ-type tests anymore (yay!) - besides the occasional competition - just know the details of each syllabus dot point. If possible, think of the answer before you look at the answer options. This is a really good one, because otherwise you get influenced by the answer options and you get confused, so it helps to actually know the answer before looking.
Ok, let's be truthful- who is honestly going to study the ins and outs of each syllabus dot point and successfully remember them? XD So just, yeah, eliminate the most incorrect options (hopefully you don't choose
them incorrectly XD ), and try and think your way into determining the most suitable answer out of the remaining options using the power of LOGIC (which hopefully doesn't fail)!!!