IT Scrutiny Query

I am a salaried employee in Pvt. Ltd companhy. I got a notice u/s 143(2) regarding for return filed for FY 2008-09, in August 2010. I personally met the assessing officer and he asked me to come with more details. After that I got a notice u/s 142(1) in May 2011 and I was asked to submit documents regarding my income, IT return, Form 16, Bank Statements, Demat account details etc, which I submitted.

Now the officer is asking for documents regarding my credit card purchases, payment of which have been made through cheque from my account and various payments made by cheque for other expenses. All these expenses are less than Rs. 10,000 each.

I would like to know:

1. Why was I chosen for scrutiny u/s 143(2) & 142(1) ?
2. Is the officer justified in seeking details of my expenses made by cheque? I thought IT was concerned about only income, exemption claimed and return filed. Once income is shown why would IT be interested in where I spend it?

Thanks,