The t-distribution can be seen in the following image:
As you can see, like the normal distribution, the t-distribution has a smooth shape, they are also symmetric. They mean of both distributions is 0.
Also, the t-distribution does not make the assumption that the population standard deviation is known.
Therefore, from the given options the one that is not a characteristic of t-distribution is option C, because the mean of the t-distribution is 0, not 1 as the option says.