The most lucrative primetime quiz show ever, ABC's "Who Wants to Be a Millionaire?," debuts Monday at 8:30 and offers each of its contestants the chance to walk away with a million dollars.

The show airs 13 out of the next 14 nights, excluding Aug. 23, when ABC intends to air the Denver Broncos-Green Bay Packers preseason game. Each night's installment is a half-hour long except those on Sundays, which begin at 8 p.m. and are one hour long. Regis Philbin hosts.

"It's a general-knowledge show in the truest sense," said executive producer Michael Davies. "We're not looking for rocket scientists or PhD's. We want real people with a broad range of knowledge and the guts to take risks on what they know and don't know."

Most quiz shows require potential contestants to pay their own way and travel to the city where the show is taped before they can even try to qualify. But "Who Wants to Be a Millionaire?" tried a new plan: Potential contestants called a 900 number and answered three multi-part general knowledge questions of increasing difficulty, entering their answers using the phone keypad. Semifinalists then moved on to a playoff game, also played by phone.

The 10 high scorers in that round, and two alternates, will show up in New York City to compete in the nationally televised round. On each of the televised programs, finalists will answer one multi-part question. The contestant who responds accurately in the fastest time can play to win up to $1 million by correctly answering up to 15 multiple-choice questions of increasing difficulty.

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NATURE "A Conversation With Koko"

Sunday at 6 on WETA, 8 on MPT

Koko, a 28-year-old western lowland gorilla, has spent most of her life at the Gorilla Foundation about 35 miles from San Francisco. The facility was co-founded in the mid-1970s by Francine "Penny" Patterson while she was earning her PhD at Stanford University.

As Koko's human friend and mentor, Patterson established a bond of trust. Over nearly three decades, she helped Koko learn sign language, building a vocabulary of 1,000 words that the gorilla used to communicate her thoughts and to express emotions such as stubbornness, sadness and even guilt. When her first pet, a kitten, died, she expressed grief and later told Patterson of her desire to have a baby of her own.

Koko's humans selected a male gorilla, Michael, as her mate, but the two bonded as siblings and have been inseparable since childhood. So, taking a cue from "The Dating Game," the humans showed Koko a video of available bachelor gorillas in zoos around the world. From them, Koko selected 6-foot, 400-pound Ndume. In the documentary, upon seeing his image, she kisses the screen and signs, "Koko love."

The foundation hopes to establish a nature preserve for the gorillas on Maui.

THE PROMISE

Sunday at 9 on NBC

In this movie, Isabella Hoffman stars as a woman seeking justice for her late sister, a domestic violence victim. Tracy Nelson plays the sister; Neil Maffin portrays the abusive husband.

Initially, Hoffman provides refuge for her sister; after her sister is killed, she raises her niece and nephew. But as she tries to make their father pay for his crime, she also grows frustrated by what she sees as faults in the justice system.

After the movie, Alex Kingston, who plays a physician on "ER," will offer a public service announcement urging viewers to get help if they're involved in an abusive relationship.