Given: Mean temperature μ = 24 , standard deviation σ =4
The lower and upper bound for temperature within one standard deviation of the mean is given by,
Lower bound = μ - σ = 24 - 4
Lower bound = 20
Upper bound = μ + σ = 24+ 4
Upper bound = 28
The temperature value between (20, 28) is said to be within one standard deviation of the mean.
From given option 27° lies in between (20°, 28°), hence 27° is the temperature value that is within one standard deviation of mean.