Complain, complains, complained, complaining

The Simple Past Tense, also called Simple Past or Preterite is a verb tense that is used to describe completed action happend in the past. It is the most basic form of past tense and it is formed by adding d, ed or ied to the base structure of the verb.

Present Perfect is a tense used to express the activity that started in the past and is still going on in the present tense. In British English this is the most used tense of them all. When you want to tell about your experience up to the present, you use Present Perfect. The prepositions that are often used with this tense are NEVER, EVER, JUST, ALREADY, YET and many others.

A transitive verb always has a noun that  receives the action of the verb, called the direct object.

An intransitive verb never has a direct or indirect object. Although an intransitive verb may be followed by an adverb or adverbial phrase, there is no object to receive its action

Present Simple is a tense used for talking about habits or activities that are constantly repeating. We also use Present Simple if we are talking about general thrust or facts about nature. This tense is also used in the Zero Conditional sentences and it is one of the most basic but also most important tenses of the English language. The most used prepositions with Present Simple are OFTEN, USUALLY, ALWAYS and many more.

REGULAR VERBS LIST