KNOW IT ALL: Tuesday’s Top 7 Stories at NBC News

Image: San Bernardino mass shooting memorial

David Siganoff (R) and his son Justin (L) pay their respects at a makeshift memorial outside the Inland Regional Center where assailants Syed Farook and wife Tashfeen Malik shot and killed 14 people, in San Bernardino, California, USA, 07 December 2015. Farook and Malik carried out the 02 December shooting in San Bernardino, in which 14 people were killed and 21 wounded. MIKE NELSON / EPA

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

1. Donald Trump Defends Muslim Ban as 'Common Sense'

Donald Trump is calling his proposal to bar Muslims from entering the United States a "temporary move." Trump said on MSNBC's Morning Joe that the idea is "common sense" and that it would not violate the Constitution — a statement at odds with legal scholars of all ideological stripes. Read more in POLITICS.

2. San Bernardino Shooters Were Radicalized for 'Some Time': FBI

Syed Farook and Tashfeen Malik, who killed 14 people at a holiday party last week, had both been "radicalized" into following an extreme form of Islam, an FBI official said Monday. "The question we're trying to get at is how did that happen, and by whom, and where did that happen ... we don't know those answers at this point," Agent David Bowdich said. Read more in NEWS.

3. Mourners Remember California Victims at Emotional Vigils

Hundreds of people gathered at the San Bernardino County Board of Supervisors building for a march and service Monday night to remember the 14 people killed in Wednesday's mass shooting. Hundreds more gathered to mourn the loss at California State University-San Bernardino, where five of the victims had attended school. Read more in NEWS.

Emotional Vigil Held for San Bernardino Victims 3:29

4. Oscar Pistorius Granted Bail for $688

A judge sprung the so-called “Blade Runner” for the equivalent of $688, but his movements from house arrest will be limited until he’s re-sentenced for murdering his girlfriend Reeva Steenkamp in 2013. Read more in NEWS.

5. Navy's Largest Destroyer Heads Out to Sea for First Time

More than 200 shipbuilders, sailors and Bath, Maine, residents gathered to watch as the largest destroyer ever built for the U.S. Navy headed out to sea for the first time. The purpose of the 600-foot, 15,000-ton USS Zumwalt's maiden voyage is to undergo sea trials through the winter. Read more in NEWS.

6. Flight From California to Paris Diverted After 'Threat'

An Air France plane traveling from San Francisco to Paris was diverted to Canada late Monday after an "anonymous threat." The flight landed safely at Montreal's Trudeau International Airport before midnight "as a precaution," according to Air France. The threat was determined to be a false alarm. Read more in NEWS.

7. 525 Dead in ISIS-Inspired Attacks Outside of Syria, Iraq Since October

In less than two months, ISIS and its sympathizers around the world have killed at least 525 people in attacks in six countries outside its so-called caliphate. Three of the attacks were actually directed by ISIS from Iraq or Syria, while two were carried out by local ISIS elements announcing their presence. In the latest, one of the shooters in San Bernardino pledged her allegiance to ISIS. Read more in INVESTIGATIONS.

Nightly Spotlight: New Cancer Drug Shows Promise

President Jimmy Carter's new cancer-free status has patients asking about the breakthrough drug he took largely credits, called Keytruda.

Jimmy Carter’s Cancer-Free Announcement Shows Power of New Drugs 1:45