C. Decreased drastically over the last five decades.
Explanation:
The cost of a given amount of computing power has decreased drastically over the last five decades. This can be proven beyond reasonable doubts with the invention of smartphones. Overtime, smartphones have become less expensive for a certain amount of computing power and easy to use.
Contrary to what was obtainable in the past where we have the large-scale Vacuum tube UNIVAC computers, ENIAC and the IBM series for computing. They weren't only big in size, they had a very small processing speed and very expensive too.
Smartphones has by far outlived the above-mentioned devices in all ramifications owing to the fact that it's relatively cheap, small in size, high processor speed and larger storage space.
I would say it is that answer because a few decades ago we needed huuuge computers that filled rooms to compute simple tasks. Now we have cellphones, which are basically computers that can fit into the palm of our hands. Our phones can do more than what those huge computers of the past did and they're easier to produce. So cost must have drastically decreased.
Since java.util.PriorityQueue doesn't use the Cloneable interface, I think it's safe to say that Serializable interfaces are implemented in all instances.
