Answer:
The topic is the titanic?
Placid means peaceful and tranquil.
The best synonym for placid would be C. peaceful.
Let's identify the reason why Mary cries when sick according to her age.
If Mary is an infant, she's crying because she probably wants water.
If Mary is an adolescent, she probably wants her Ma.
If Mary is an adult, she cries when she's sick because she is tired.
So, how old is Mary?