Answer:
For the first question, the two most important determinants of price elasticiy of demand would be:
The answer for the second question is "likely to have relatively elastic demand". A good with elastic demand is a good whose demand changes a lot when the price changes. Consider sodas for example. A soda of a particular brand has many substitutes, and if the price of, for example, coca cola goes up, people can still buy pepsi, or sprite, or mountain dew, then, the demand for coca cola will fall.
For the third question, the answer is "a heart valve for heart attack victims", because this type of medical device is highly complex and practically has no substitutes, besides, it is a vital necessity. Even if the price rises 100% in one month, a patient will still do as much as possible to buy it.