Answer:
A). Trial 1, because the average rate of the reaction is lower.
Step-by-step explanation:
The first sentence elaborates that 'trial 1 had a lower level of concentration of the reactant that eventually led the reaction's average rate to fall.'
A trial having a higher level of concentration of a specific reactant will cause the concentration's average rate to rise. As per the graph provided, trial 2's average reaction rate is higher which shows that its concentration is greater and more reactive. However, the opposite happens in trial 1 where the amount of reactant is lesser in the concentration that leads the concentration to possess a lower rate of reaction. Thus, option A is the correct answer.