What's the next in the series?

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

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

Spot what is wrong here in below Picture?

If 21x = 79x, what is the value of x?

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

You need to climb ten stairs. At every stair, you can either take one step up or you can jump two steps up.

In how many different ways you can climb 10 stairs?

Alex is stranded on an island covered in forest.
One day, when the wind is blowing from the west, lightning strikes the west end of the island and sets fire to the forest. The fire is very violent, burning everything in its path, and without intervention the fire will burn the whole island, killing the man in the process.

There are cliffs around the island, so he cannot jump off.

How can the Alex survive the fire? (There are no buckets or any other means to put out the fire)

A man calls his dog from the opposite side of a river. The dog crosses the river without a bridge or a boat and manages to not get wet. How is this possible?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _