Read the following article and answer the question. Article: It's certain:for twins,life really does imitate art.My twin brother,Kirk,and I grew up being constantly mistaken for each other.Classmates,friends,teachers,even relatives couldn't tell us apart. As a result,we were often unfairly punished or rewarded. Eventually,we learned how to use the Mistaken Identity Syndrome (MIS) to our advantage.For example,we would play tricks on our friends and classmates,pretending to be the other twin.Nor were teachers immune to our tricks.On at least one occasion,when Kirk was sick,I covered for him by taking his tests.We also tried our little game out on Mom,but she always knew who was who.Once we grew up,we even covered for each other at work.We didn't mean any harm;we simply started this as an experiment to see whether our bosses and co-workers could tell the difference. As a bank manager, I meet with dozens of clients on a daily basis, while my brother manages a staffing service for local employers. As a result, Kirk is constantly approached by people who want to discuss their various money accounts, while I'm frequently thanked on the street as a department store customer service representative. However, the MIS took a truly embarrassing turn when Kirk and I found ourselves unable to tell each other apart. Once, my brother and I were traveling in a car with several friends. My brother's hair must always be in place. Kirk was driving when he noticed in the rearview mirror that his hair was a bit messy. He lifted his right hand to brush his hair back into place and was disturbed when his hand didn't appear in the mirror. Several times he repeated this action. Finally, he started laughing. Question: It can be inferred that when the author covers for his brother at work,_. Answer:
Available choices: a). he is often successful; b). he means to harm his boss; c). his brother is seriously ill; d). he often behaves strangely;
a).