Read the following context and choose the best option to answer the question.
Context: I even snuck in a trip to the cake decorating store , but was disappointed they were out of everything I need for a cake . Thankfully it 's not for a few weeks , so hopefully they 'll get what I need in . Sunday we went to Front Royal and went canoing on the river with a large group . It was fun , mostly . I ' m very sore in the back and shoulders today , however .
Question: Why am I in pain today ?
Options: 
- Because I overindulged in birthday cake .
 - Because I got into a fight at a store .
 - Because I 'm unused to rowing .
 - None of the above choices .


Because I 'm unused to rowing .