74. The quality / public transport/ services / Vietnam / should / improve /. A. The quality of public transport services in Vietnam should been improved. B. The quality of public transport services in Vietnam should being improved. C. The quality of public transport services in Vietnam should was improved. D. The quality of public transport services in Vietnam should be improved. 75. Many countries /already using /solar energy. A. Many countries is already using solar energy. B. Many countries was already using solar energy. C. Many countries are already using solar energy. D. Many countries were already using solar energy. 70. They will show flying cars to the public when they finish it. A. Flying cars will be shown to the public when finished. B. Flying cars will be show to the public when finished. C. Flying cars will being shown to the public when finished. D. Flying cars will be showing to the public when finished. Mình cần giải thích ạ