a. Both sentences are expressed clearly. However, the sentences could be improved by replacing "students" with "subjects" in order to be more specific about who the instructions were read to.
b. The first sentence is clear, but the second sentence could be clearer and more direct by stating, "We read the instructions to reduce experimenter bias."
c. The first sentence does use a first-person pronoun, but the use of "we" is appropriate in this context.
d. This statement is not a problem with the clarity of the original sentences, but is a suggestion for improvement.
e. Both sentences are not unclear, but as mentioned above, they could be improved by being more specific about who the instructions were read to.