One Common Grammar Mistake

One of the most common grammar mistakes that i always make is the word " had ". I am always confused between the words (has and had) and (have and had).

Has is a verb.
Has is singular simple present.
Have is prular of the word has.
Had is used as simple past and past participle .

1. Example between has and have:

-I have two sisters.
-The dog down the street has a lax owner.

2. Example between have and had.
(auxiliary verb, taking a past participle) Used in forming the perfect aspect and the past perfect aspect.
-I have already eaten today.
-I had already eaten.

EXERCISE USING HAS, HAVE AND HAD.

1.I ___ a house and a car.

2.I'm going to ___ some pizza and some Pepsi right now.

3.I ___ already eaten.

4.She ___ him arrested for trespassing.

5.He ___ completed his homework today.

6.The hospital ___ several patients contract pneumonia last week.


Answers:
1.have
2.have
3.had
4.had
5.has
6.had