zero and first conditionals

FILL THE GAPS WITH THE CORRECT VERB FORM:Doplňte správný tvar sloves, použijte zkrácené tvary a proto použijte anglickou klávesnici (apostrof pro stažené tvary don't, doesn't / won't je klávesa se znakem § na klávesnici české) - českou čárku vám program opraví jako chybnou. 1.- You get ( get ) twenty if you multiply ( multiply ) ten by two.2.- If a machine is ( be ) properly maintained, it never fails ( fail / never ) .3.- If you brush ( brush ) your teeth every day, they are ( be ) healthy and nice.4.- I will leave ( leave ) him a message if he isn´t (not / be) home when I phone.5.- They won’t come ( not / come ) to the wedding if they don’t get ( not / get ) the invitation on time.6.- If little children have ( have ) pets, they develop ( develop ) a sense of responsibility.7.- You will improve ( improve ) your English if you spend ( spend ) some time in Britain.8.- People call ( call ) the fire brigade if there is ( be ) a fire in the house.9.- You will need ( need ) a lawyer if you have ( have ) any legal problem.10.- You get ( get ) water if you mix ( mix ) hydrogen and oxygen.11.- If you behave ( behave ) like that, you won’t go ( not / go ) to the zoo12.- If somebody is ( be ) a vegetarian, he doesn’t eat ( not / eat ) meat.13.- I will accept ( accept ) your invitation if I am ( be ) available on that date.14.- If you sleep ( sleep ) well, you rest ( rest ) your body and mind.15.- You will take ( take ) the dress back to the shop if it doesn’t fit ( not / fit ) you.16.- If you don’t have ( not / have ) any more questions, we will finish ( finish ) the meeting here.17.- If you cross ( cross ) an international date line, the time changes ( change ).18.- She always locks ( lock ) the front door if she leaves ( leave ) the house.19.-There will be ( be ) a lot of problems if we don’t help ( not / help ) with the work.20.- If you heat ( heat ) metal, it expands ( expand ).