Final answer:
The horizontal asymptote of the function f(x) = −3(2)^x−5 is y = -5, as that's the value the function approaches as x tends to infinity.
Step-by-step explanation:
To find the horizontal asymptote of the exponential function f(x) = −3(2)^x−5, we need to examine the behavior of the function as x tends to infinity. As x increases, the term −3(2)^x grows exponentially, but no matter how large it gets, the subtraction of 5 will always leave us with a resulting value that does not include the negative infinite term; thus, the function approaches the horizontal line y = −5 as x tends to plus or minus infinity. Therefore, the correct answer is c. y = -5.