REDWOOD CITY, Calif. (AP) — Sega of America Inc., the world’s No. 2 maker of videogames, will become the first to use movie-style ratings to alert parents that some games may be too violent or sexually suggestive for children.Sega will assign one of three ratings beginning in August: GA for general audiences, MA-13 for mature audiences with parental discretion advised, and MA- 17 for adults only. Sega said it was particularly concerned about the level of realism offered by its new CD-ROM game machine, which enables participants to interact with movie-quality clips of real actors instead of animated figures. Toys R Us decided against selling the CD game “Night Trap” in Britain or Canada because of its graphic content. In the game, attackers dressed in black stalk scantily clad girls. Unless rescued by the player, the girls are murdered. No. 1 Nintendo won’t follow suit, saying its own development guidelines are sufficient.