Which One of the Following Students Is Most Clearly Engaging

Which one of the following students is most clearly engaging in critical thinking?

A) Louise has a puzzled look as she reads her textbook."I don't understand what the author is trying to say," she thinks.
B) Before turning in his astronomy test, Sam rereads his responses to the test's three essay questions."I'm pretty sure I answered the first two questions correctly," he tells himself, "but I'm not sure about the last question."
C) Raul jumps at the chance to learn how to use desktop publishing software."I'm particularly interested in learning how to integrate text and graphics," he tells his teacher.
D) As Morgan watches her lab partner experiment with a pendulum, she says, "You just changed the length of the string at the same time you added more weight.That won't tell us anything."