Explanation:

- Red Cross Society persuading to donate blood: This can be marketed. The Red Cross uses campaigns to encourage blood donation, highlighting the need and benefits to both donors and recipients.

- Kerala Tourism persuading people to visit Kerala for health tourism: This is also marketable. Tourism boards promote destinations, showcasing attractions and benefits like health and wellness offerings to attract visitors.

- Political parties persuading to vote for a particular candidate: This too can be marketed. Political campaigns use marketing strategies to influence voters' perceptions and garner support for candidates.

- All of the above are correct since each involves a form of marketing or promotional activity.