Answer:
C). Although
Step-by-step explanation:
The most adequate transition word to begin the third sentence would be 'although' as it helps in denoting that irrespective of the plentiful numbers of cellphone users, the majority is intercepted from the associated consequences. This transition word helps in bridging the gap between the ideas and helps in making the smooth transition from one idea to another irrespective of the difference. Thus, option C is the correct answer.