1. High birth rate and high death rate with poor medical services (B): In the early and mid-20th century, India experienced a phase characterized by a high birth rate and a high death rate. During this period, the birth rate was relatively high due to traditional family structures and social norms that encouraged larger families. However, the death rate was also high due to limited access to healthcare and medical services, poor sanitation, and infectious diseases. This phase resulted in a steady but relatively slow population growth.

2. Steady population growth (D): India entered a period of steady population growth. This phase saw a gradual improvement in healthcare and a reduction in the death rate due to advancements in medical services, better sanitation, and disease control measures. While the birth rate remained relatively high during this period, it was balanced by the declining death rate, resulting in a steady increase in the population.

3. Population explosion (A): The population explosion phase came after the steady population growth phase. This period is characterized by a sharp increase in the birth rate, particularly during the mid-20th century. Factors contributing to this included a large young population, limited access to family planning, and cultural factors that encouraged larger families. 

4. Population growth rate remained high with gradual slowing down (C): Subsequently, India entered a phase where the population growth rate remained high, but it gradually began to slow down. During this phase, efforts were made to control population growth through family planning and awareness campaigns. While the birth rate remained relatively high, there was a gradual reduction in family size due to increased awareness and access to contraceptives. This led to a slowing down of the population growth rate.

Therefore, option 2 is correct.