【答案解析】The world has entered the age of knowledge explosion. According to incomplete statistics, the total amount of knowledge worldwide doubles every five years. The convergence of many fields doesn't mean the decrease of new knowledge. No one can master all the continuously-updated knowledge related (relating / associated / connected with) to his job (profession / occupation). It is by no means easy (far from easy) to keep oneself informed of the latest development in his sphere of research.