Which of the following is a compound-complex sentence?

1. ক
   I went to the store, and I bought some milk.
   
2. খ
   Because I was tired, I went to bed early.
   
3. গ
   Although I like to read, I haven't had time lately, and I am behind on my work.
   
4. ঘ
   The cat slept on the mat.