- 'Phase-I' of population growth in India is defined by a period of stagnation, where high birth and death rates result in low or negative net population growth (Option II).
- A rapid decline in mortality rate (Option III) is typical of later population growth stages, not Phase-I, making it an incorrect descriptor for this phase.
- Inadequate health and medical services (Option IV) contributed to the population growth stagnation in Phase-I, as India faced substantial healthcare and infrastructure deficiencies during this period.
Therefore, the correct answer is (C) Only I, II, and IV are correct.