4) Employee stock options (ESOs) have been compared to regular stock call options (SO).

Among the similarities are (chose one):

a) ESOs and SOs can be bought and sold.

b) ESOs and SOs can be calls or puts.

c) ESOs and SOsrise in value when volatility increases.

d) ESOs and SOs typically expire in a few years or less.

e) ESOs and SOs typically vest in a few days to weeks.

f) Other Specify.