<文意選填>第21至30題為題組 In the early days of the film industry， actors themselves shot acrobatic acts and dangerous scenes， until they began to get injured. There were， however， no ___23___ crew members to perform impressive stunts at that time. (A) possible (B) sensation (C) risky (D) cost (E) witnessed (F) professional (G) called for (H) tried out (I) necessity (J) career
