How to use "A" an "An" ?

1. The articles a and an is used in certain expressions of quantity with singular countable noun.
2. Use A  before all words that begin with consonant sounds:

• Examples: A door, a pen, a dog, a house, a bus.

     * Some words may be spelled with vowels but be pronounced with consonant sounds:

• Use A when u makes the same sound as the letter y in the word you: a union, a unicorn.
• Use A when o makes the same sound as the letter w in the word won: a one-legged man.
• Do not use A when the h is silent.

     3. Use An  before all words that begin with vowel sounds:

• Examples: An indian, an apple, an eagle, an egg.
• Use An before a silent h: an hour.
• Use An before word that are spelled with consonants but pronounced with vowel sounds: an MBA.

Practice

http://www.learnenglishfeelgood.com/english-indefinite-articles2.html

http://www.englishexercises.org/makeagame/viewgame.asp?id=1203

http://www.eslgamesplus.com/a-an-the-spin/

Modals of Possibility

Modals of Present Possibility

• Modal verbs as Might, May, Could and Must are different ways to say maybe or we use it when we want to make a guess about something.

      Examples:

1. She might be at home.
2. I may be late.
3. The keys could be in the car.
4. You must go to the doctor.

• Could and can are used to ask questions about present possibility. Might is very uncommon. Use be in short answers to questions containing be.

       Example: - Could she be working?     She might be.

                       - Can it be true?  It must not be.

• Will and won't  when we are very sure.

        - They will be at home now.

• Should | Shouldn't are used when we want to make an assumption about something that is probably true. Also we used it when we want to give an advise. 

         -You shouldn't do that, it's dangerous.

         - My husband should be there by now.

Practice

http://speakspeak.com/english-grammar-exercises/intermediate/intermediate-grammar-exercise-modal-verbs-for-present-probability-must-cant-could-may-might

http://www.learnenglish-online.com/grammar/modals/tests/modalspossibility.html

http://www.curso-ingles.com/practicar/ejercicios/modals-1

                         

The Passive Voice

We use the passive voice when we want to put the objet first or maybe we don't want to say who did the action.

Sometimes what causes the action is unknown, unimportant, or obvious.

Example

• Active: I painted the house.
• Passive: The house was painted.

In passive voice you need the verb to be and the past participle.

Tense	Active	Passive
present simple	I make a cake.	A cake is made (by me).
present continuous	Karla is cleaning the house.	The house being cleaning by Karla.
past simple	Luis read Harry Potter.	Harry Potter was read by Luis.
past continuous	She was writing an e-mail.	An e-mail was being writing by her.
present perfect	I have made a mistake.	A mistake has been made by me.

Practice

http://www.curso-ingles.com/practicar/ejercicios/the-passive-voice

http://www.saberingles.com.ar/curso/lesson24/06.html

http://www.ejerciciosinglesonline.com/new-exercises/ex-1-passive/

Present Perfect

We use the Present Perfect to say that an action happened at an unspecified time before now; the exact time is not important; the action happened at any time up to the present.

Form: 

              Subject + Has/Have + Past Participle

Example: You have studied psychology.

                 You haven't studied psychology.

Yes or No question with short answer:

Have you studied psychology?

• No, I haven't.
• Yes, I have.

Information question:

Wh + have/has + subject + past participle

 Where have you studied?

The past participle of regular verbs is the same as the simple past form ( verb + -ed ); irregular verbs have special past participle forms.

Practice:

http://www.curso-ingles.com/practicar/ejercicios/present-perfect

http://www.ejerciciosinglesonline.com/new-exercises/ex1-presente-perfecto-simple/

http://www.ejerciciosinglesonline.com/exercises-and-theory/ex1-present-perfect/