Final answer:
The statement is true; an undamped spring-mass system will resonate if subjected to repeated impulses at intervals matching its natural period.
Step-by-step explanation:
The statement that an undamped spring-mass system exhibits resonance-like behavior when it is excited by repeated impulse functions at intervals equal to the natural period of the system is true. Resonance occurs when a periodic force drives a harmonic oscillator at its natural frequency. The natural frequency is the frequency at which a system will oscillate if not affected by driving or damping forces, and applies to both forced and free vibration scenarios. In the case of forced vibration without damping, like the undamped spring-mass system mentioned, if driven at its natural frequency, the system will indeed resonate, which means it will potentially oscillate with increasing amplitude.