1.  It was the drug that (kill) Paola. She still (be) alive today if she (not take) that drug.

It was the drug that KILLED Paola. She WOULD still BE alive today if she HAD NOT (HADN'T) TAKEN that drug.

2.  Dr. Robbins never patented his invention. If he (patent) it he (make) a lot of money.

Dr. Robbins never patented his invention. If he HAD PATENTED it he WOULD HAVE MADE a lot of money. 

3.  I (not recognise) Doris at first because she (wear) sunglasses. If she (not wear) them I (recognise) her immediately.

I DID NOT (DIDN'T) RECOGNISE Doris at first because she WAS WEARING sunglasses. If she HAD NOT (HADN'T) BEEN WEARING them I SHOULD (WOULD) HAVE RECOGNISED her immediately. 

4.  My nephew Freddy (be) never interested in games. If he (play) games like the other boys he (be) happier at school.

My nephew Freddy WAS never interested in games. If he HAD PLAYED games like the other boys, he WOULD HAVE BEEN happier at school.

5.  Our sister (refuse) the job in spite of the high salary. She (refuse) even if the company (offer) her twice as much.

Our sister REFUSED the job in spite of the high salary. She WOULD HAVE REFUSED even if the company HAD OFFERED her twice as much.