Answer:
a. was engineered as an oncovirus, only infecting tumor cells.
Step-by-step explanation:
Oncoviruses such as the engineered herpes virus is used a tool for killing cancer/tumor cells. When a virus infects a cancer cell, it makes several copies of itself within the cancer cells until the cell burst. The oncoviruses only target tumor cells, it does not affect healthy normal cells.
In addition to infecting tumor cells, it also triggers the immune system against the cancers.