Question $2($Mandatory$)(0\mathrm{.}5$ points$)$

What major set$-$back did the field of gene therapy encounter?

The viral delivery method ended up making people sick from the virus.

The gene therapy delivery methods were unsuccessful, and patients in the trials did not show any changes compared to the controls.

It became illegal in the U$.$S$.$ to carry out any gene therapy research.

In $1999$ the unexpected death of a young gene therapy patient halted human gene therapy trials and led to a slowing of progress in this field.