Step-by-step Solution:

\[ \textbf{Debugger is a program that:} \] \[ \begin{array}{ll} \textbf{A.} & \text{allows to set breakpoints, execute a segment of program, and display contents of registers} \\[6pt] \textbf{B.} & \text{links object code to produce an executable} \\[6pt] \textbf{C.} & \text{does not allow step-by-step execution of a program segment} \\[6pt] \textbf{D.} & \text{compiles source code to object code} \end{array} \] \[ \textbf{Correct Answer: A} \]