SERIES

Tough as Nails (N) 8 p.m. CBS The 100 (N) 8 p.m. CW United We Fall Jo (Christina Vidal) steps in as a role model for her niece (Olivia Taylor Cohen), much to the teenager’s father’s (Guillermo Díaz) dismay. 8 p.m. ABC Big Brother The unscripted series launches a new season with a cast of past winners, finalists and memorable personalities. 9 p.m. CBS Coroner This Canadian import, adapted from a book series by M.R. Hall, stars Serinda Swan as a recently widowed Toronto coroner who has a teenage son (Ehren Kassam). 9 p.m. CW Guy’s Grocery Games Four finalists throw a beach ball to determine which aisles they get to shop. 9 p.m. Food Network Mar vel’s Agents of S.H.I.E.L.D. With Kora’s (Dianne Doan) help from the inside, Sibyl (Tamara Taylor) and Nathanial (Thomas E. Sullivan) continue their efforts to shape a dark new future while staying one step ahead of the agents. 10 p.m. ABC Marrying Millions The documentary series that looks at couples where the partners come from vastly different socioeconomic statuses returns for a new season. 10:03 p.m. Lifetime Corporate (N) 10:30 p.m. Comedy Central