Answer
a. Yes, it is almost certain. Two heads would come up, on average, on one out of every $2^{2} = 4$ throws.
b. It is less likely. All ten coins come up heads, on average, on one out of every $2^{10} = 1024$ throws.
c The chances are essentially zero, even if every human did this for the age of the universe.
All ten thousand coins come up heads, on average, on one out of every $2^{10000}$ throws. This is a number that starts with "199..." and has 3011 digits in all. In case you are wondering, the editors at Gradesaver consulted a program known as Wolfram Alpha to bring you that fun fact.
