Which statement best describes the overall trend in the data from 1900 to 2000?

• A. The number of resistant species decreased in most intervals
• B. The number of resistant species remained the same
• C. The number of resistant species increased over time
• D. The number of resistant species fluctuated randomly with no trend

Answer: (C)

The main idea is to identify the overall direction of change in a time-series: does the count go up, stay the same, fluctuate without a clear path, or go down? If the data show more resistant species as years progress from 1900 to 2000, the overall pattern is an increase over time. This makes sense biologically because selective pressures—like the widespread use of antibiotics and pesticides—favor individuals with resistance traits. Those individuals survive and reproduce, spreading resistance and raising the number of resistant species as time goes on. Even if some intervals show little change or small dips, the long-term trajectory is upward, which is why describing the trend as increasing over time best fits the data.