Research on Lock-Out Provisions on Cable Television Have Shown That

Research on lock-out provisions on cable television have shown that

A) they are quite successful at helping parents screen shows based on content.
B) they are are not as successful as hoped in helping parents screen shows based on content.
C) they are quite unsuccessful at helping parents screen shows based on content.
D) they are easy to understand for parents, but parents just don't want to use them.