Never know this matter, to practice is to emphasize that the acquisition of correct understanding comes from practical activities, so I chose C. Option A's viewpoint "development motivation" emphasizes that new problems appear in practice and need new understanding to solve them, thus promoting the development of understanding, but this question obviously does not emphasize new problems in practice and new development of understanding, so it is ruled out. Option b emphasizes the guiding role of cognition in practice, while this question emphasizes the role of practice in cognition, so it is excluded. Error in option d, both direct experience and indirect experience are very important, so rule it out.