Which of the following speeds should not be exceeded when fording with a D7R dozer?

When fording with a D7R dozer, maintaining a speed of 3-4 mph is essential for safe operation. This speed range allows the operator to maintain control over the machine while minimizing the risk of water displacement that could affect stability. Operating at this controlled speed aids in navigating through water and prevents the dozer from becoming unstable or submerged in deep water. Additionally, fording at higher speeds could result in a loss of traction or unexpected water resistance, which could be dangerous for the machine and the operator. Therefore, choosing the speed range of 3-4 mph is optimal for ensuring safe and effective fording with the D7R dozer.