Although I wouldn't particularly call this question type an inference q, despite the question stem, the answer to this question is quite obvious that it almost seems alarmingly wrong.
We need to find something between the relationship of the African-American population and the law in the Chesapeake Bay region of Virginia in 1650-1670.
Making notations throughout the passage helps pinpoint the answer to this question relatively easily. However, since we just read the passage, the numbers 1650 & 1670 should point to exactly where to look for.
The answer is from lines(44-49). Since we know that the proportion of African-Americans were increasing, we also know that the laws regarding them increased as well. For example, the passage mentions that it increased laws regulating interracial relations and again mentions a statute that bans baptism from changing slave status (1667).
Knowing this we can easily choose answer choice B that states that the percentage of blacks citizens as did the legal restrictions against them.