What do we learn about Dr. Yuka Sasaki doing her research? （ ）

A、Shefoundbirdsanddolphinsremainalertwhileasleep.
B、Shefoundbirdsanddolphinssleepinmuchthesameway.
C、Shegotsomeideafrompreviousstudiesonbirdsanddolphins
D、Sheconductedstudiesonbirds’anddolphins’sleepingpatterns.