How do managed placements on the Display Network work?

How do managed placements on the Display Network work?

A)  Advertisers can guarantee placement on prominent and popular sites.
B)  Advertisers manually select the desired sites on which their ads may appear
C)  Keywords are used to place ads next to content that matches the ad.
D)  Appropriate sites are automatically chosen for the advertiser by the Google AdWords system.

Answer : Advertisers manually select the desired sites on which their ads may appear

Reason : 

Managed placements-

A targeting method you can use to specifically choose websites, videos, and apps that are part of the Google Display Network where you'd like to show your ads. Unlike other targeting methods, like keywords or topics where your ads are placed on sites automatically for you (reported in your account as automatic placements), you select managed placements yourself.

Read more at https://support.google.com/adwords/answer/99502?hl=en