The answer will be A. Harmful it says it in the definition.
Answer: Therefore
Explanation: Therefore means that 'as a result' , 'thus', 'consequently'
As we can see here, there is an excuse of Mrs. Eaton saying what she has to do today, meaning that these stuff (doing laundry, walking the dog and so on) show us how busy she is. So, the sentence "I'm busy" shows that she is busy with doing/completing these stuff.
Space travel is the next step B
