下面哪一项建议策略能够鼓励尽可能多的网站访问者分享其电子邮件地址？

Using Single Sign-On (SSO) tools like Google or Facebook Connect significantly increases email address sharing because it simplifies the process for users. Instead of manually typing their email and creating a new password, they can log in with a single click using existing, trusted credentials. This convenience reduces friction and builds trust, leading to higher conversion rates for email collection. The other options are less effective: placing the request only on the checkout page limits opportunities; adding pop-ups can be intrusive and annoying, potentially deterring users; and offering better deals via email, while a good retention strategy, doesn't directly increase the initial collection rate as much as SSO.