Nina wanted to know whether different brands of soda hold different levels of carbonation. She observed people opening sodas over several weeks. Nina concluded that some brands hold more carbonation because they were more likely to foam when opened. Which of the following best describes the evidence Nina gathered through her observations?

a) Nina’s observations are sufficient to form a scientific conclusion.

b) Nina could use her data to form a hypothesis and test it with an experiment.

c) The data from Nina’s observations led her to an incorrect scientific conclusion.

d) Nina should disregard her observations because they did not result from a controlled experiment.