Final answer:
When starting up a steep grade, you should usually shift into first gear to utilize the maximum power and torque available for climbing. This assists in maintaining momentum and preventing the vehicle from stalling.
Step-by-step explanation:
When starting up a steep grade, it is generally best to shift into first gear. This is because first gear provides the most power and torque, which is necessary for climbing steep inclines. Shifting into a higher gear too soon might cause the vehicle to struggle and lose momentum. It's also important to take into account the type of vehicle and its load, as these factors can influence the appropriate gear selection for ascending a steep hill.