This is only a possible version; you can create other correct sentences with the same structure
Exercise 1: causes of congestion in megacities
The reason why traffic congestion in megacities is increasing is because of the excessive growth of vehicle numbers that growing population brings.
Exercise 2: causes of overpopulation
Today, the advanced science have offered better medical facilities, promoted fertility treatment, and brought down death rate. This results in increasing population growth and becoming overpopulated gradually.
Exercise 3: cyber crime
Cyber-crime is another by-product of technology advancement which poses threat to the social security; internet fraud, online piracy and spread of violent and pornographic content create great risks which are available easily on the web without screening, causing harm to the social order.
Exercise 4: cause and root cause of obesity
Some people believe that obesity is a result of inactive life, as this causes less exercise and over eating.
Exercise 5: cause and effect of social media
Development of social networking resulting from technological advancement and fast-paced modern life poses serious social concerns, considering gradually alienated relationship between people, as well as deteriorated interpersonal communication skills.