Step 1: Define the economic sectors, especially the advanced ones.
Tertiary: Basic services (Transport, Communication, Retail).
Quaternary: Knowledge-based services (IT, R& D, media).
Quinary: The highest level of decision-making in an economy. It includes top-level executives in government, science, universities, non-profits, healthcare, culture, and the media.
Step 2: Analyze the options.
Transport and Communication are part of the tertiary sector.
"Services" is a broad term, but generally refers to the tertiary sector.
Policy formation is a high-level decision-making process carried out by top government officials and leaders. This fits the definition of the quinary sector perfectly.