Concept:The phrase "economical with the truth" means being sparing or careful about revealing all the facts.
Explanation:The word "economical" means using very little of something, such as money or resources.
Here, it means the people used very little of the truth.
Therefore, they did not tell the whole truth.
They kept back some facts because they were not willing to reveal everything.
This makes "knew more than they were prepared to say" the correct interpretation.
Answer:D. They knew more than they were prepared to say