You use "in" when you mean "in" and you use "or" when you need to use "or". It is rather difficult to construct rules for the use of prepositions in most languages.The grammatical structure of the...
Using " Has " is referred a past tense. Such as: He has taken the garbage out already. Using " Is " for example is referred a Present tense. Such as: He is taking out the garbage.
Has and have are two forms of the infinitive to have Has is used for he, she and it, and generally speaking third person singular. (eg Richard has a lot of friends) Have is used for all other case...