question: Why are odd but not prime numbers chosen for the length of ZC (Zadoff Chu) sequences? option 1: To achieve better auto and crosscorrelations under fractional timing and frequency offsets option 2: To reduce computational complexity at the UE option 3: To achieve better synchronization between the UE and the BS option 4: To allow multiple UEs to send control information at the same time and frequency option 5: To achieve better robustness to collisions in the random access channel 