The growth of bacteria (lactobacillus) in milk leads to curd formation. A minimum bacterial population density of 0.8 (in suitable units) is needed to form curd. In the graph below, the population density of lactobacillus in 1 litre of milk is plotted as a function of time, at two different temperatures, 25 degrees C and 37 degrees C. Consider the following statements based on the data shown above: i. The growth in bacterial population stops earlier at 37 degrees C as compared to 25 degrees C. ii. The time taken for curd formation at 25 degrees C is twice the time taken at 37 degrees C. Which one of the following options is correct? A. Only i B. Only ii C. Both i and ii D. Neither i nor ii

GATE 2017 · General Aptitude · Line Graph · medium

Answer: Only statement i is correct. The growth in bacterial population stops earlier at 37°C than at 25°C. The correct answer is A.

1. Evaluate Statement i: plateau time comparison: From the graph, the 37°C curve visibly flattens and becomes horizontal at a smaller time value than the 25°C curve. The 37°C bacteria stop growing earlier. Statement i is TRUE.
2. Evaluate Statement ii: curd-formation time ratio: From the graph, the 37°C curve crosses density = 0.8 at approximately t1 hours, and the 25°C curve crosses at approximately t2 hours. The graph shows t2 is NOT exactly double t1 (the ratio is closer to 1.5 to 1 than 2 to 1). Statement ii is FALSE.
3. Select the correct option: Only statement i is correct, which corresponds to option A.