Final answer:
The incorrect statement about the Dred Scott decision is that Scott was granted his freedom; in fact, the Supreme Court ruled that he remained enslaved and that blacks could not be U.S. citizens.
Step-by-step explanation:
The student's question is about the Dred Scott decision, which was a landmark Supreme Court case in 1857. The correct statements regarding the case are that Dred Scott and other blacks could not be citizens of the United States (Option a), Congress had no authority to stop or limit the spread of slavery (Option b), and Scott had to remain a slave (Option c). Therefore, the statement that is not correct concerning the Dred Scott decision is Option d: Scott was granted his freedom. In reality, the Supreme Court ruled that Dred Scott remained enslaved, and the decision further reinforced the institution of slavery in the United States before the Civil War.