Which is the tallest tree in the world?

In $Pinus$,the female gametophyte develops only from:

Resin ducts are found in:

Select one of the following pairs of important features distinguishing $Gnetum$ from $Cycas$ and $Pinus$ and showing affinities with angiosperms.

Cycas stem shows:

Gymnosperms maintain their dominance over angiosperms in which of the following regions?