**Core Concept**
The crude birth rate is a demographic measure that reflects the number of live births per 1000 people in a given population over a specific period, usually a year. This rate is influenced by factors such as fertility rates, population size, and age distribution.

**Why the Correct Answer is Right**
To calculate the number of pregnant females, we need to understand that the crude birth rate represents the number of live births per 1000 people. Given that the crude birth rate is 30 per 1000 people, we can assume that this rate applies to the entire population of 5000 people. To find the number of pregnant females, we need to divide the total population by 1000 and then multiply the result by the crude birth rate.

Using the formula: (Total population / 1000) * Crude birth rate
= (5000 / 1000) * 30
= 5 * 30
= 150

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
The crude birth rate is an important demographic measure that can help healthcare providers and policymakers understand the needs of a population, particularly in terms of maternal and child healthcare.

**Correct Answer:** 150