time lines. >> reporter: security another challenge. here special forces train for potential terrorist attacks on a bus line. really high crime and violence remain the biggest threats in rio. it is also not clear if the subway extension connecting venues will be done on time but rio officials are confident they will meet the targets and visitors will be won over by the city's natural beauty and charming residents. shaps shasta darlington cnn, rio de janeiro. >> will rio be ready? we will have to wait and see. thank you for joining us. i'm george howell. stay with us. we will have more from moscow as mourners are set to march in honor of slain opposition activist boris nemtsov. the news continues next hour here on cnn u.s. and cnn international.