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?
1 Uses. 2  The present perfect subjunctive is used in the same types of clauses as the present subjunctive, and normally is used: to indicate the action as completed with governing verbs in the present or future tense or command forms. 3  Examples: Me alegro de que ella haya llegado.4  I'm glad she (has) arrived. Adverbial clauses (time, purpose, etc.). 2  Remember that the subjunctive is used when the action in the adverbial clause is viewed as anticipated or hypothetical. 3  Again, contrast the present time and past time situations: Lo haremos cuando vengan. ( 4 present) We'll do it when they come.