To determine the appropriate domain for the problem, we need to consider what the variable \( t \) represents in the context of the bacteria growth equation \( n(t) = 50(1.2)^t \). Here, \( t \) is the time in hours, and we are interested in observing the number of bacteria after a specific duration.
Given that the scientist is checking the population in 4 hours, the relevant values for \( t \) should range from the start (0 hours) up to the point of observation (4 hours). Therefore, the appropriate domain for \( t \) should be represented as all values from 0 to 4 hours.
Among the provided options, the one that matches this reasoning is:
Option #3: 0 ≤ t ≤ 4
Options #1 and #2 do not match because they extend beyond the specified time frame of observation. Option #4 is incorrect as it represents a range for \( n \), not \( t \).