Which One of the Following Is the Best Example of a Hidden

Which one of the following is the best example of a hidden curriculum as educators typically use the term?

A) To make each week's spelling words more interesting, a third-grade teacher always adds a few "seasonal" words (e.g., Halloween, Thanksgiving, valentine) to the words identified as "Grade 3 words" in the school district's spelling curriculum.
B) A social studies teacher encourages his students to read the newspaper every night. He tells his students, "To do well in this class, you can't just study your textbook. You also have to be aware of current events in your local community and around the world."
C) A science teacher gives tests that focus largely on defining scientific terms, and she gives credit only for definitions that are identical to those in the textbook. In doing these things, her students begin to think that "learning" means memorizing things word-for-word.
D) When students in a math class work on complex word problems, their teacher insists that they show the steps they use to arrive at their answers. She tells them, "That's the only way I can see whether you're thinking about these problems in the same way a mathematician might."