Answer:
Matilda eats Cereal on Monday.
Step-by-step explanation:
Breakfast options for Matilda are: Cereal (C), Bread (B) or Yogurt (Y).
Condition 1: If she eats cereal and bread she also eats yogurt.
Then Matilda's breakfast combination is: C + B + Y.
Condition 2: If she eats bread or yogurt, she also eats cereal.
Then Matilda's breakfast combination is: C + B or C + Y.
Condition 3: She never eats both cereal and yogurt.
Then Matilda's breakfast combination does not include is: C + Y.
Condition 4: She always eats bread or cereal.
Then Matilda's breakfast combination always includes is: C or B.
If Matilda eats bread (B) then according to Condition 2 she eats cereal (C) also. And since she eats both C and B she eats yogurt (Y) also.
But according to Condition 3 Matilda never eats both cereal and yogurt.
Hence she can never have all three for breakfast.
She cannot eat bread (B) alone [according to Condition 2], Matilda is left with only one option, i.e. Cereal (C).
Thus, Matilda eats Cereal for breakfast on Monday.