If you say my name, I will no longer exist. What am I?

Find the missing letter in the last circle logically in the given below picture.

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

What can you hold in your right hand, but never in your left hand?

What is the centre of gravity?

Rob is taller than Edwin, and Jurgen is shorter than Rob.
Of only one of the following statements, we now certainly know it is correct:

A.Edwin is taller than Jurgen
B.Jurgen is taller than Edwin
C.It cannot be determined if Jurgen or Edwin is the tallest.

The current time can be represented by below textual rebus.

0
=========
B.Sc
LLB

Can you tell us the current time?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

The centre of the third figure is empty. What digit should fit inside?

Two friends were stuck in a cottage. They had nothing to do and thus they started playing cards. Suddenly the power went off and Friend 1 inverted the position of 15 cards in the normal deck of 52 cards and shuffled it. Now he asked Friend 2 to divide the cards into two piles (need not be equal) with equal number of cards facing up. The room was quite dark and Friend 2 could not see the cards. He thinks for a while and then divides the cards in two piles.

On checking, the count of cards facing up is same in both the piles. How could Friend 2 have done it ?