Thomas (a researcher) took a random sample of 50 residents in a neighbourhood and found that the average height of the citizens was 170 cm. Suppose that the team is made aware of the fact that the distribution of heights of the city's residents is distributed normally. Which of the following statements about the estimator(s) are true?

1. 1. The sample mean is an unbiased estimate of the average height of the city's residents.
   2. The sample median is an unbiased estimate of the average height of the city's residents.
   3. The sample median is an biased estimate of the average height of the city's residents.
   4. The sample mode is a biased estimate of the average height of the city's residents.