What is the product formed when N,N-Dimethylaniline reacts with Nitrous acid in cold conditions? 

4-Nitroso-N,N-dimethylaniline 

The correct answer is option 1. 4-Nitroso-N,N-dimethylaniline.

When N,N-Dimethylaniline reacts with nitrous acid in cold conditions, the product formed is primarily 4-Nitroso-N,N-dimethylaniline.

In this reaction, the nitrosation occurs predominantly at the para position relative to the dimethylamino group due to its electron-donating nature, which makes the para position more reactive towards electrophilic substitution.

So, the correct answer is: 4-Nitroso-N,N-dimethylaniline