KNOW IT ALL: Monday's Top 6 Stories at NBC News

Image: Malaysian Airline MH370 six month anniversary
Young passengers take a picture of Malayisa Airline aircraft using their mobile phone at Kuala Lumpur International Airport (KLIA) in Sepang outside Kuala Lumpur, Malaysia, 08 September 2014. It's been six month since the dissappearance of Malaysia Airlines flight MH370 while en-route from Kuala Lumpur to Beijing with 239 people on board. The plane vanished on 08 March. AHMAD YUSNI / EPA

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Good morning, and happy Monday. Here are some of the stories we're following today:

1. Prince William and Kate Middleton expecting second baby

"Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their second child," royal officials said in a statement, adding that the family is "delighted" with the news. Prince George, who was born in July of last year, has been learning how to share and interact with other children as of late, so he should be fully prepared to be a great big brother. Read more in NEWS.

2. Obama will reveal strategy to combat ISIS this week

In an exclusive interview with Chuck Todd on NBC's "Meet the Press," President Barack Obama said he will address the nation on Wednesday to outline how the U.S. is going to deal with the threat of the terror group ISIS, in Iraq and Syria. "We are going to systematically degrade their capabilities," Obama said, but reiterated that he will not advocate for the deployment of U.S. ground troops. Obama also spoke with Todd about immigration reform, the Ebola outbreak and the "theater" of the presidency. Read more in POLITICS.

3. Joan Rivers ‘would have loved’ her send-off

Joan Rivers' funeral in New York on Sunday was attended by TV personalities, actors, singers, comedians and fashion icons. And outside, fans and press gathered to catch a glimpse of the temple where the ceremony was held. Access Hollywood host Billy Bush said the funeral was "irreverent," but "Joan Rivers would have loved it." After all, Rivers, who died Thursday at 81, wrote in a 2012 book that she wanted her send-off to be "Hollywood all the way." Read more in POP CULTURE.

4. Still no sign of MH370, six months later

On March 8, 2014, Malaysia Airlines flight 370 dropped off of the radar with 239 people on board. That was six months ago. Still, not a piece of debris, a shred of clothing or any sign of the jet has been detected, despite millions of dollars and countless hours spent searching for it. A U.S. Navy captain has said the search could go on for years, but the Australian Transport Safety Bureau is hoping a new phase focused on a mapped-out "priority area" will yield something — and provide a little closure for the families of the passengers and crew. Read more in NEWS.

5. Hundreds of kids land in hospitals due to uncommon virus

Health officials in 10 states have reached out to the Centers for Disease Control and Prevention for help to figure out whether a surge of an uncommon respiratory virus in children is something to be concerned about in the long-term. Many of the illnesses appear to be caused by enterovirus D68 or EV-D68 — a distant cousin of the polio virus — and are causing breathing complications for the kids. Read more in HEALTH.

6. Serena Williams wins sixth U.S. Open; men’s final tonight

Serena Williams defeated Caroline Wozniacki 6-3, 6-3 in a 75-minute final to win her 18th Grand Slam title and sixth U.S. Open crown on Sunday. Williams now ties greats Chris Evert and Martina Navratilova for fourth on the Grand Slam list. Meanwhile, in a men's final no one predicted, Marin Cilic and Kei Nishikori square off Monday after vanquishing top seeds Novak Djokovic and Roger Federer in semifinal upsets. Read more in SPORTS.

What’s trending today?

What kind of pictures are usually taken at a concert? Blurry, grainy shots of the stage, with or without the performer. Photographer Angelina Castillo turned away from the stage at a recent One Direction concert and decided she would take pictures of the dads in a sea of screaming tween girls. The dads' emotions — written all over their faces — clearly range from frightened to disgusted, and the resulting photos are hilarious.