c) simple present for future

Present Continuous & Present Simple for the Future
source: EnglishTeacherMarc         2017年11月26日

Present simple as a future tense
Your English Web          2016年12月17日
For interactive online courses: https://curious.com/yourenglishweb

Using the future continuous and ‘be’ with the infinitive
source: BBC Learning English         2015年12月1日
more practice activities: http://www.bbc.co.uk/learningenglish/...

Present Simple and Present Continuous for the Future
source: Practice English with Paul         2015年6月27日
A lot of interesting posts by me: http://vk.com/id290352757

Future tense (using Present Continuous & Present Simple)
source: Mrs English   2012-02-28