Which of the Following Is the Best Summary of the Current

Multiple Choice

Which of the following is the best summary of the current state of gene therapies, such as the use of retroviruses?

A) The theoretical work about how such processes might work is still incomplete.
B) Gene therapies have been developed but ethical concerns have prevented their use in humans at the present time.
C) Gene therapies have been developed and tried, but with limited success so far.
D) Gene therapies are used routinely with very good success in treating a number of genetic diseases.