ii)Transition metals and their compounds show catalytic activities because of Variable or multiple oxidation states, ability to form complexes, they provide large surface area for adsorption.

I think the best technique for memorizing is by assigning meaningfulness to things that are to be memorized.

Or in other words, relating things with a memorable story, simply, creating a story.
Do you remember yourself teaching us to memorize things easily. We had related words to a story and almost everyone in the class remembered at least 25 words among the total of 30. I still remember "Bhachyeko Haat". Haha!

Memory export Jim Kwik says that anything combined with emotion becomes a...

No, if three vectors do not lie in a plane, they cannot give zero resultant.

Explanation:

Let A, B and C be three vectors. If they give zero resultant, then

     A+B+C=0

or, A= -(B+C)

Hence, they will produce zero resultant, if A is equal to negative of vector (B+C). The vector (B+C) lies in the plane of B and C. Hence, A will be equal to negative of (B+C) if A, B and C all lie in a plane.