Translate these sentences in the proper tense form:
1) я зараз пишу листа
2)до того часу як ти прийшов, я написав листа
3)я пишу листа вже дві години
4) я напишу листа завтра

the history of science fiction films parallels that of the motion picture industry as a whole, although it took several decades before the genre was taken seriously. since the 1960s, major science fiction films have succeeded in pulling in large audience shares, and films of this genre have become a regular staple of the film industry. science fiction films have led the way in special effects technology, and have also been used as a vehicle for social commentary.

science fiction films appeared very early in the silent film era. the initial attempts were short films of typically 1 to 2 minutes in duration, shot in black and white, but sometimes with colour tinting. these usually had a technological theme and were often intended to be humorous. one such short was le voyage dans la lune, created by georges méliès in 1902. often considered to be the first science fiction film, it drew upon jules verne and h. g. wells in its depiction a spacecraft being launched to the moon in a large cannon. its ground-breaking special effects pioneered the way for future science-fiction films, and it became largely popular after its release.science fiction literature would continue to influence early films. jules verne's classic 20,000 leagues under the sea was adapted multiple times, notably into the 1916 film, one of the first feature-length science fiction films. others, such as edison studios' 1910 adaptation of mary shelley's novel frankenstein, and the 1913 adaptation of robert louis stevenson's dr. jekyll and mr. hyde, brought the concept of mad scientists to cinema. these two also demonstrated an early overlap between the science fiction and horror genres. into the 1920s, another success was the lost world, based on sir arthur conan doyle's book of the same name. it was one of the earliest examples of stop-motion animation, and also introduced several now-famous science fiction concepts, like monsters, dinosaurs, and hidden worlds.oddly, in the 2000s (decade), sf films seemed to turn away from space travel, and fantasy predominated. except for star trek and star wars films, the only films set off earth that appeared in the first half of the 2000s (decade) were serenity and the poorly received mission to mars and red planet. on the other hand, fantasy and superhero films abounded, as did earthbound sf such as the matrix reloaded and matrix revolutions.

science fiction has returned to being a tool for political commentary in recent times with films like a.i. artificial intelligence and minority report with the former questioning the increasing materialism of today's world and the latter questioning the political situations surrounding the world post 9/11. unique entries into the genre were also released around this time with the first science fiction romance eternal sunshine of the spotless mind.by the middle of the decade, the theater audience had begun to decline and this was reflected in the numbers attending the science fiction movie releases of this period. sophisticated home theater systems came close to matching the cinema experience, and avoided the expense and inconvenience. film studios had begun placing product advertisements prior to the start of films in theatres, seeking another means to enhance their bottom line, and alienating a segment of the theater-going audience. making up for the losses in cinema revenue, were sales and rentals of the high-quality dvd releases, many of which included previously cut scenes and extra material.

1) I'm writing a letter now.

2) By the time you came I had written a letter.

3) I've been writing a letter for two hours.

4) I will write a letter tomorrow.