Tough, difficult and arduous are synonymous. Choose, select and pick are synonymous. Option, variant and choices are synonyms too. The difference b/n "choose" and 'pick" and "select'. Как выбирать, набирать, подбирать и т.д. English is fun, just like Russian. Choose comes from the word, "choice'. Pick means to choose, and also to pick up, to lift up only one of the items; and select has to do with preference because 'lect' has the meaning of something delightful. Arduous is like Latin for our word 'hard' and refers to hard work, difficult work or task. Difficult is the usual word to use, and we use the word 'difficulty' as a synonym for 'problem' or a temporary blockage. "tough' can have the sense of жёсткий especially for a hard surface (like a watermelon) or is it as in the skin is difficult to cut/ Options are when there are several things (choices) to choose from. "variant' is not used like in Russian. A variant is a statistical thing when the results vary (they differ) from the other results. A variant is when something is a little unusual, and not as common, especially for plants. Sorry that I can't explain it well. Like Russian, there are several words to choose from, and some are more common in some situations than in other situations.