Three reasons why bull market is alive and well

Traders on the floor of the New York Stock Exchange.
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Two weeks ago, the turned negative for 2015 and some investors began to speculate as to whether this would be the year when the bull market ends.

Since then, stocks have marched higher as the Federal Reserve gave more of a dovish tone on interest rate hikes and Greece appeared to make some concessions to creditors.

Also behind the rally: a number of Wall Street strategists came out in defense of the bull market.

Among this group, here are the three most common reasons why the advance is alive and well and some ways they said to play it.