A Researcher Is Working to Generate a New Cancer Drug

A researcher is working to generate a new cancer drug. Thus far, he has identified a compound that can reduce the size of tumors in the lung. However, in order for the drug to work, the lung tumor has to be small. In addition, the tumor cannot have metastasized (spread to other areas of the body) . Furthermore, he knows that the drug acts to prohibit the signaling from one tumor cell to another tumor cell. Given the above information, this new drug prohibits:

A) autocrine signaling between tumor cells.
B) synaptic signaling between tumor cells.
C) paracrine signaling between tumor cells.
D) endocrine signaling between tumor cells.