Conditional Sentences Part I

Adrian   Mon Oct 17, 2005 4:45 am GMT
The following sentences I came across in grammar books and references, but some of them sound incorrect to me. I am not sure.


He never says a word unless he feels he’s being threatened in someway. (Why did we use the passive progressive (is being threatened) and not the passive (is threatened) in the conditional clause?

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What’s the difference in the meaning between the following sentences? When do we use each form?

(1)
If you drive carefully, you’ll have fewer accidents.
If you drove carefully, you would not have so many accidents.


(2)
If you help me now, you’re a true friend
If you helped me now, you would be a true friend


(3)
if she found a job, she’ll be happy.
If she found a job, she was happy.


(4)
if they didn’t show him the way, he will not find the right office
if they don’t show him the way, he will not find the right office.


(5)
if it rains tomorrow, be sure to close the windows
if it rains tomorrow, be sure to close the windows


(6)
if the truth were known, public opinion would change
if the truth were known, public opinion will change



(7)
if you don’t brush your teeth carefully, you’ll have many cavities.
If you didn’t brush your teeth carefully, you would have many cavities.


(8)
Even if they offered to pay, I wouldn’t accept any money from them.
Even if they offer to pay, I will not accept any money from them.
Even if they offered to pay, I will not accept any money from them.


(9)
in case you want me, I’ll be in my office
in case you wanted me, I’ll be in my office


(10)
Without me to supplement your income, you wouldn’t be able to manage
Without me to supplement your income, you won’t be able to manage


(11)
if you ever touch me, I’ll scream
if you ever touched me, I would scream


(12)
She’s taking a stick with her in case she has any trouble on the way
She’s taking a stick with her in case she had any trouble on the way


(13)
if you believe that, you will believe anything
if you believed that, you would believe anything
if you believed that, you will believe anything


(14)
They sat on the grass if it was fine
They sat on the grass if it were fine


(15)
if it was raining, we usually stayed indoors.
If it rained, we usually stayed indoors.
If it rained, we would usually stay indoors
If it was raining, we would usually stay indoors


(16)
if the tap is dripping, it needs a new washer.
If the tap drips, it needs a new washer.


(17)
if nuclear weapons are employed in a world war, the world will be destroyed
if nuclear weapons were employed in a world war, the world would be destroyed


(18)
if anything happens, I’ll return immediately
if anything happened, I’ll return immediately
if anything should happen, I’ll return immediately


(19)
if anyone should come this way, we would be caught like rats in a trap
if anyone should come this way, we will be caught like rats in a trap
if anyone comes this way, we will be caught like rats in a trap


(20)
if he goes, I will go too.
If he were to go, I would go too
If he went, I would go too
If he goes, I would go too