1) “The Challenge: USA” debut, 9:30- 11 p.m., CBS. Here’s CBS’ key newcomer for the summer. It takes 28 previous contestants from four reality shows, giving them super-sized physical challenges. (Shown here, Lee Temory and Tiffany Mitchell descend from a skyscraper.) Some of these people are already winners; that includes three “Survivor” champions (Tyson Apostol, Ben Driebergen and Sarah Lacina) and one apiece from “Amazing Race” (James Wallington), “Love Island” (Justine Ndiba) and “Big Brother” (Xavier Prather).
2) “Big Brother” season-opener, 8-9:30 p.m., CBS, And this show continues CBS’ effort to make Wednesday its big reality night. It will air at 8 p.m. Wednesdays (with “Challenge” at 9, starting next week), 9 p.m. Thursdays and 8 p.m. Sundays. Tonight, Julie Chen Moonves introduces the new housemates and the new look of their house.
3) “The Green Planet” opener, 8 p.m., PBS. At 96, David Attenborough keeps finding new worlds. Most of his time has been in the animal kingdom, but this five-part series focuses on plants. Using slow-motion, robotically triggered cameras, it gets footage that wouldn’t have been possible earlier in his career. The result is both informative and, often, stunningly beautiful. PBS follows with “Nova” at 9 p.m. and the “Expedition with Steve Backshall” season-opener at 10, with Backshall viewing brown bears in Russia’s Kamchatka Peninsula.
4) “Mysteries Decoded” season-opener, 8 p.m., CW. Surrounded by the gorgeous Rhose Island landscape, a house offers an eerie history. It was built in 1736; people claim that seven children have died there and that it’s haunted. That was the basis for the 2013 movie “The Conjuring” and its sequels. Now hour brings back people depicted in the film. It tries hard, but rarely gets past someone saying it feels creepy. For a fun variation, stick around for “Wellington Paranormal” at 9, with a drolly funny “Where’s Waldo” take-off.
5) “Abbott Elementary,” 9 p.m., ABC. Barbara is the one teacher who has everything under control – until the school suddenly demands a computer-learning set-up. For Janine, this may finally be a chance to help her older colleague. For Barbara … well, the result is funny, but strains believability.