End face mechanical seal - Seal categories. 1  All mechanical seals must contain the four elements described above but the way those functional elements are arranged may be quite varied. 2  Mechanical seals are generally classified into two main categories: Pusher or Non-Pusher.
User: Which verb form is used to indicate present perfect tense? verb or verb-s will verb have verb-ed have verb-ingWeegy: The verb form is used to indicate the perfect progressive tense is: have + been + verb + -ing weegy2x|Points 179|User: Which statement about a letter of complaint is true?
We make the Present Perfect tense with the correct form of the auxiliary verb have (have/has) and the third form (past participle) of the mail verb. To form the past participle of the regular verbs, we add ed to the infinitive.Examples: I have worked as a secretary for two years. Present Continuous Tense when to use; how to form; ing forms of the verbs; English action and state verbs; the difference between the Present Continuous and the Present Simple tenses; test. 2  The verb to be-the Present Simple Tense. 3  Grammar reference and online exercises for Elementary level.