Adrug researcher could avoid risking human health in tests of new drugs by applying the new drugs to cultures of human cells and observing the effects. using computers to select and notify potential subjects for tests on the new drugs. conducting a trial on patients, using only very small dosages and short lengths of exposure to the new drugs. only testing the new drugs on volunteer subjects who have tried all available treatments with no success.

The answer is only testing the new drugs on volunteer subjects who have tried all available treatments with no success. Only applying to cultures of human cell can not get the reliable results.

The correct answer would be "using computers to select and notify potential subjects for tests on the new drugs".

The following steps are used to test a drug:

First, they are tested using computers (in silico drug designing) in which molecular dynamics or mechanisms are used to determine the strength of intermolecular interactions.  Once the lead compound has been found, it is tested on human cells in in-vitro conditions. Drugs which pass the above tests are tested on animals. Testing a drug on humans is the last step of a drug test. In this, a drug is tested on a small group of volunteers to check the efficiency, dosage, and side effects of the drug.