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KNOW IT ALL: Friday's Top 7 Stories at NBC News

Trump and Cruz took aim at Trump on Thursday night.

Good morning. Here are some of the stories we're following today:

1. Rubio, Cruz Put Aside Differences and Gang Up on Trump

It took eight months and three electoral losses in a row, but the Republican presidential field finally woke up and realized Donald Trump was not going to defeat himself. Thursday’s CNN-Telemundo debate was the first time Sens. Marco Rubio and Ted Cruz, who have savaged each other in the last several meetings, put aside their differences and focused 100 percent of their fire on Trump. Read more in POLITICS.

2. Trump: I Can't Release Tax Returns Until Audits Are Done

Donald Trump cited ongoing tax audits as the reason he is delaying releasing his tax returns despite pressure from former GOP nominee Mitt Romney. During Thursday night’s Republican debate in Houston, the billionaire said he will “absolutely” release his return, “but I’m being audited now for two or three years, so I can’t do it until the audit is finished, obviously, and I think people would understand that.” Read more in POLITICS.

3. Four Dead, Including Gunman, 14 Injured in Kansas Shootings

Four people were killed, including the gunman, and 14 others were injured after a series of shootings Thursday in rural Kansas, authorities said. Police remained in a standoff with the gunman's roommate Thursday night several hours after the gunman was killed. Read more in NEWS.

4. Al Qaeda Makes Comeback in ISIS' Shadow

A resurgent al Qaeda is emerging from the shadows. While ISIS has been soaking up headlines, its older sibling has been launching attacks and grabbing territory too, and U.S. intelligence officials tell NBC News they are increasingly concerned the older terror group is poised to build on its achievements. Read more in NEWS.

5. Reformers vs. Hard-Liners: It's Election Day in Iran

Iranian voters went to the polls Friday in an election that could set the stage for a reformist comeback or see hard-liners tighten their hold on the country. State TV showed long lines of people waiting to cast their ballots in the twin elections as the polls opened. Read more in NEWS.

6. Zika Might Cause Worse Birth Defects Than Feared

The case of a Brazilian woman whose unborn baby died may show that Zika is causing even worse birth defects than feared, doctors reported Thursday. The fetus had virtually no brain at all, and died seven months into the pregnancy, the doctors reported. Read more in HEALTH.

7. N.Y. Students Who Claimed Racial Attack to Face Charges

Three university students who claimed they were victims of a racially-motivated attack on a bus in Albany, New York, will now face charges for assault and misleading police about the alleged incident. Read more in NEWS.

8. Joe Biden to Introduce Lady Gaga at the Oscars

Vice President Joe Biden will join pop star Lady Gaga on stage at the Oscars on Sunday to spotlight the issue of campus sexual assault. Biden will introduce Lady Gaga’s performance of “Til It Happens to You,” a nominee for best original song, according to a White House official. The song was featured in the documentary “The Hunting Ground,” which deals with campus rape.