Nuclear Energy

Energy

http://www.childrensuniversity.manchester.ac.uk/interactives/science/energy/what-is-energy/

Present Perfect exercises- For & Since

http://www.ecenglish.com/learnenglish/lessons/present-perfect-with-for-and-since

https://www.englishclub.com/grammar/verb-tenses_present-perfect_fs.htm

http://www.agendaweb.org/grammar/for-since-exercises.html

http://www.englishpage.com/verbpage/verbs5.htm

http://www.perfect-english-grammar.com/present-perfect-exercises.html

Present Perfect with for & since