Which of the following plants is called stinging nettle?

Select the correct match.
$(a)$ Cinchona officinalis $(i)$ Rhizome
$(b)$ Rauwolfia serpentina $(ii)$ Bark
$(c)$ Curcuma longa $(iii)$ Root

$Piper \text{ } betle$ is the botanical name of:

The source of cotton is

Axillary buds are used to raise a crop of:

Hevea brasiliensis is a source of