#### Answer

a)See below.
b)Sample mean, sample variance and sample proportion.
c)True.

#### Work Step by Step

a)An unbiased estimator is a statistic where the mean of the estimator's sampling distribution is equal to the corresponding parameter's mean.
b)The sample median and sample range are biased estimators, whilst the sample mean, sample variance and sample proportion are unbiased estimators.
c)The sample variance is an unbiased estimator (see above) and the sample standard deviation is the square root of the sample variance, hence it is true.