What's the only room from which no one can enter or leave

What's the next in the series?

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

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

The measurement of time, That can't be found on a clock, But can be looked upon on a map.

Who is He ?

In a supermarket, there is an intelligent glass pane before a refrigerating unit. This glass pane allows cherries and apples through it but does not allow grapes and Orange to pass through it.

Can you identify the rule that the glass pane is following?

_ _ _ IE _ _
_ _ _ IE _
_ _ IE _ _
_ _ IE _
_ _ _ _ IE

Like you see, some letters have gone missing from these words that contain the IE pair at some or the other place. The letters that will be used to fill the blanks are given below. Use them and form meaningful words. Can you do that?

A, C, D, F, H, K, L, M, N, N, O, R, R, S, S, S, T, T, Y and Y.

Find the missing number in the image below.

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

Which alphabet letter is a question?

Why is a river so rich ?