 Complete the following phrase:  Some groups held a 7.21 Half Anniversary rally in Tin Shui Wai with the theme Guard the Truth, Dont Forget 1856  721. At about 7:30 pm, about a hundred citizens participated, some wearing school uniforms or black clothes and wearing masks. At the scene, joint signing sessions and Lennon paintings were set up to allow participants to write their opinions and signatures. At least four police cars and dozens of police officers were seen around the rally. The rally began in the form of a drama about the citizens 39 minutes of waiting for the police at the 