Answer: A. True
Explanation: Cell receptors are proteins that receive signals and trigger a signal cascade for the cell can respond. There's many types of receptors, depend of their location and their enzymatic activity, and each type can recognize certain signals. For example, tyrosine-kinase receptors can recognize growth factors, JAK associated receptors can recognize cytokines, etc. That specificity is given by the structure of the receptor and the structure of the signal.