curve, curves, curved, curving

The Simple Past Tense, also called Simple Past or Preterite is a verb tense that is used to describe completed action happened 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 Continuous is a tense used for activities that are happening in the moment of speaking. It also can be used in a future aspect for future arrangements or plans. This tense is always used when you are describing a picture. The most used prepositions used with Present Continuous are AT THE MOMENT and NOW.