Ответ:

• If the sun shines, we always go for a walk
• if the sun shines , we will go for a walk
• if the sun shined , we would go for a walk
• If the sun had shined , we would have gone for a walk

• If we have time we always visit our friends in London
• if we have time we will visit our friends in London
• if we had time we would visit our friends in London
• if we had had time we would have visited our friends in London

• if you eat a lots of sweets you will always have a toothache
• if you eat a lot of sweets you will have a toothache
• if you ate a lot of sweets you would have a toothache
• if you had eaten a lot of sweets you would have had a toothache

• if they invite their best friends they always cheer them up
• if they invite their friends they will cheer them up
• if they invited their best friends they would cheer them up
• if they had invited their best friends they would have cheered them up