a) The p-value of a test is the probability that the null hypothesis is true.
False.
b) A difference in expression which is highly signifcant must be biologically relevant.
False: could be some kind of "clock"
c) Large samples are bad because small differences can be signifcant.
False. Having a more significant result is not a bad thing
d) A difference in expression which is signifcant can still be due to chance.
True, but very unlikly.