List of top Data Interpretation & Logical Reasoning (DILR) Questions on Critical Reasoning

A researcher claims that eating breakfast improves concentration in schoolchildren. Which of the following, if true, would most strengthen this claim?
Advertisement: 'Nine out of ten dentists recommend BrightSmile toothpaste. Therefore, BrightSmile must be the best toothpaste available for everyone.' The reasoning in the advertisement is most flawed because it
Manager: 'Employees who attended our new training program showed a 15 percent increase in productivity. Therefore, we should make the training program mandatory for all employees.' Which of the following, if true, most weakens the manager's argument?
A city introduced a new bus rapid transit system, and within a year traffic congestion in the city center fell by 30 percent. The transport minister concluded that the new bus system was responsible for reducing the congestion. Which of the following, if true, most weakens the minister's conclusion?