Write the next sentence in this paragraph:

How to hack gmail 
Understand the limitations. 
Gmail is an incredibly secure service. The only way you'll be able to " hack " into someone's account is by stealing their password.

Options are:
(a). You will need to make sure that you actually have a password that is valid, or that could slip from someone's system. To be successful, you must be able to, or at least to know..
(b). If your target has two-factor authentication, you'll need their mobile device as well. There is no other way around two-factor authentication..
(c). You must be a " good " user to hack a gmail account. This means to use this service only online..
(d). To hack someone's password, simply click the " hack " button beside the user name. Once prompted, enter your password, then click " confirm..
(b).