No load shall extend ____________ in front or ____________ in the rear.

The correct answer indicates that no load shall extend three feet in front of the vehicle and four feet in the rear. This limitation is set to ensure safety on the road. Loads that extend beyond the rear can create visibility issues for other drivers and increase the risk of accidents. By capping the front extension at three feet, it helps to minimize the likelihood of interfering with pedestrian pathways and ensures the load does not obstruct the vehicle's maneuverability or visibility.

Additionally, Texas law dictates specific measurements for protruding loads to maintain an orderly flow of traffic and enhance safety. The specified limits help drivers to gauge the space they need to occupy on the road and manage their vehicles accordingly, giving other drivers sufficient room to safely navigate around them.

In examining the other potential answers, they do not align with these safety standards as they propose either shorter or longer extensions, which could lead to higher risks of accidents or logistical challenges in transportation.