Select all the following which are true. Marking: canvas marks as follows: If there are k correct answers, and you select answers of which X are correct, and X are incorrect, then Your mark is X X2 k k The x-distribution is the sum of squared standard normal distributions. The X-distribution is the sum of independent standard normal distributions. The F-distribution is the ratio of two x-distributions. The t-distribution is the ratio of a standard normal and a x-distribution. The t-distribution is the ratio of a standard normal and a x-distribution, divided by its degrees of freedom. The x-distribution is the sum of independent, squared standard normal distributions. The F-distribution is the ratio of two x-distributions, each divided by its degrees of freedom. The t-distribution is the ratio of a standard normal and the square root of a x-distribution divided by its degrees of freedom. The F-distribution is the square root of the ratio of two x-distributions, each divided by its degrees of freedom.