**Core Concept**
Crude birth rate (CBR) is a measure of the number of live births occurring among a population of 1,000 people per year. It's an essential demographic indicator used to assess the reproductive health of a community.

**Why the Correct Answer is Right**
To calculate the number of pregnant females, we need to use the crude birth rate (CBR) formula: CBR = (Number of live births / Population) x 1000. Given that the CBR is 30 per 1,000 people, we can rearrange the formula to find the number of live births: Number of live births = (CBR / 1000) x Population. Substituting the values, we get Number of live births = (30 / 1000) x 5000 = 150. Since each birth is associated with a pregnant female, the number of pregnant females is equal to the number of live births.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it doesn't use the given CBR to calculate the number of live births.
* **Option B:** This option is incorrect as it's a random number and not calculated using the CBR formula.
* **Option D:** This option is incorrect because it doesn't consider the given population size of 5000 people.

**Clinical Pearl / High-Yield Fact**
When calculating the number of pregnant females using the CBR, remember to use the formula: Number of live births = (CBR / 1000) x Population, and then assume each birth is associated with a pregnant female.

**Correct Answer:** 150