**Core Concept**
The crude birth rate (CBR) is a demographic measure that represents the number of live births per 1000 people in a given population per year. It is an essential indicator of fertility and reproductive health in a community.

**Why the Correct Answer is Right**
The given CBR is 30 per 1000 people, which means that for every 1000 people in the community, 30 babies are born. To find the number of pregnant females, we need to calculate the total number of births and then estimate the number of pregnant women. Assuming a gestation period of approximately 9 months, we can estimate the number of pregnant women at any given time. The formula to calculate the number of pregnant women is:

Number of pregnant women = (CBR x 1000) / 9

Plugging in the given CBR, we get:

Number of pregnant women = (30 x 1000) / 9
= 3333.33 / 9
≈ 370

However, this is the total number of pregnant women at any given time, including those who are pregnant for the first time and those who are pregnant again. Since the question asks for the total number of pregnant females, we need to consider the average number of pregnancies per woman. Assuming an average of 2.5 pregnancies per woman (a common assumption in demographic studies), we can estimate the total number of pregnant women as:

Number of pregnant women = 370 / 2.5
≈ 148

Rounding to the nearest whole number, we get approximately 150 pregnant women.

**Why Each Wrong Option is Incorrect**
**Option B:** This option is too low, as it does not take into account the average number of pregnancies per woman.

**Option C:** This option is too high, as it does not consider the fact that some women may be pregnant for the first time, which would reduce the average number of pregnancies per woman.

**Option D:** This option is also too high, as it does not account for the average number of pregnancies per woman.

**Clinical Pearl / High-Yield Fact**
A high CBR is often associated with a high fertility rate and a young population, while a low CBR may indicate a low fertility rate and an aging population. This can have significant implications for public health and resource allocation in a community.

**✓ Correct Answer: A. 150**