Colin uses his phone for everything, so he likes to keep it with him at all times. lately, though, he's found it difficult to concentrate when he's studying because people often call him or send him a text message. what should colin do to improve his concentration?

Turn off his phone.

Explanation:

The best thing Colin could do, by far, is to turn off his phone when he is studying. It seems that Colin has an issue concentrating because he is constantly interrupted by his phone, as people are always calling him or sending him a message.  If he continues with this system, Colin will find it really difficult to perform a lot of tasks, as he will struggle with concentration. Moreover, everything will take a little bit longer and he will be more likely to make mistakes.

i don't know sorry i cannot read a novel in 30 min.

explanation:

but just in case i think the answer is b.