VERBS AND PRESENT PROGRESSIVE

The present progressive is used in English for to talk about situation that's happening at moment. For example: I'm eating. This a situation that I'm doing in a moment.

FORM :  AM/ARE/ IS + VERB + ING

AFFIRMATIVE SENTENCES

I'm writing a letter

The scientist are developing a experiment

NEGATIVE SENTENCES

I'm not writing a letter

The scientist aren't developing a experiment

INTERROGATIVE SENTENCES

Am I writing a letter?

Are the scientist developing a experiment?

TO PRACTICE

http://en.educaplay.com/en/learningresources/1109294/present_progressive_.htm