The proliferation is increase in total number of content. For example, in the above case proliferation of text messaging has alarmed their parents to take measures to reduce it.
The other words such as ambiance or summarization (making a conclusion) are not applicable to this proliferation.
Thus, the options (c), (d) and (b) are incorrect.
The proliferation is increase in total number of content. For example, in the above case proliferation of text messaging has alarmed their parents to take measures to reduce it.
Therefore, the correct option is – a. increase.