Final answer:
The slope of the linear equation that models the submarine's descent is -10.5 ft/s, and the y-intercept is -50 feet below sea level. Therefore, the correct answer is B) Slope: 10.5 ft/s, Y-Intercept: -50 ft.
Step-by-step explanation:
The submarine's rate of descent at 10.5 ft/s represents the slope of the linear equation since it is the rate of change in depth per second. The starting point, 50 feet below sea level, serves as the y-intercept because it is the depth at which the descent begins when time is zero seconds.
To model this situation as a linear equation y = mx + b, where y is the depth in feet, x is the time in seconds, m is the slope, and b is the y-intercept, we can set m to be -10.5 and b to be -50. Therefore, the slope is -10.5 ft/s, and the y-intercept is -50 ft, which corresponds to answer choice B.