The correct option is B Thursday
Let's identify the day on which Rosy ate the minimum number of apples.
So, let's count the number of apples eaten by Rosy on each day.
On Monday, Rosy ate 7 full apples and 1 half apple.
∴ Fraction of apples eaten by Rosy on Monday = 712.
On Tuesday, Rosy ate 5 full apples and 1 half apple.
∴ Fraction of apples eaten by Rosy on Tuesday = 512.
On Wednesday, Rosy ate 6 full apples and 1 half apple.
∴ Fraction of apples eaten by Rosy on Wednesday = 612.
On Thursday, Rosy ate 4 full apples and 1 half apple.
∴ Fraction of apples eaten by Rosy on Thursday = 412.
Hence, Rosy ate the least number of apples on Thursday.