Indirect questions - When reporting questions, the reporting verbs say or tell are replaced by ask, inquire, wonder or want to know.
Concord of Tenses
If the main verb is in a past tense, the verbs in the subordinate clause expressing simultaneous activity must be in a past tense as well. Examples It was raining when I come to the train station last night.
Progressive Forms In The Passive Voice
In English language two progressive forms in passive are used. The Present Progressive Passive I am being asked .The Past Progressive Passive
Defective Verbs + Perfect Infinitive
When defective verbs are followed by have + past participle, they indicate a past action. That action was not fulfilled or other way round.
Need – Dare
Defective verbs - Need / ni:d / and Dare. The ver need is used as a defective verb and as a regular verb. The defective verb need has only the present tense, takes no -s in the 3rd person singular.
Must – Ought – Should
Must express a necessity, a command or a probability. Ought to and should express moral obligation or a probability. Verb ought is more emphatic than verb should. Verb should is often used when subject is asking or giving advice. Also should often indicates a recommendation rather than obligation.
Can & May
Can and May, are two verbs that have only the past tense and the present tense. Verbs may and can express - ability, capability.
BE + TO-INFINITIVE
The construction be + to-infinitive also denotes a future activity already planned. This form also denotes obligation, intention or what should be done.
GOING + TO-INFINITIVE
The form going + to-infinitive denotes a future activity already arranged, or decided upon. This form is very common in English for expressing such an action.