A bridge is designed to withstand various loading conditions, including live loads and dead loads. Which of the following correctly defines live load and dead load in the context of bridge engineering?

a$)$ Live load refers to the weight of the bridge structure itself, while dead load refers to the weight of movable objects on the bridge.

b$)$ Live load refers to temporary loads on the bridge caused by vehicles, people, or natural events, while dead load refers to the permanent weight of the bridge structure and any fixed objects.

c$)$ Live load refers to the impact of environmental factors such as wind and seismic activity on the bridge, while dead load refers to the fluctuating traffic loads.

d$)$ Live load refers to the dynamic forces exerted on the bridge during construction, while dead load refers to the static forces acting on the bridge during its service life.