PRACTICE:
https://www.allthingsgrammar.com/uploads/2/3/2/9/23290220/atg-quiz-firstcon-r1.pdf
http://mbonillo.xavierre.com/exercises/eso2/2esowint09/Firstcond2eso3.htm
http://www.english-4u.de/cond_clauses_ex1.htm
http://mbonillo.xavierre.com/exercises/eso2/2esover09/firstc2e1.htm
http://www.saberingles.com.ar/curso/lesson19/05.html
https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises
https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises?02
http://mbonillo.xavierre.com/exercises/eso2/2esowint09/Firstcond2eso3.htm
http://www.english-4u.de/cond_clauses_ex1.htm
http://mbonillo.xavierre.com/exercises/eso2/2esover09/firstc2e1.htm
http://www.saberingles.com.ar/curso/lesson19/05.html
https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises
https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises?02