Here are the correct forms of the verbs in parentheses for each sentence:

44. He's waiting for his mother to come back from Chicago. If his mother **comes** home, he **will have** a lot of presents.
45. He wanted to buy some Christmas presents but he couldn't. If he **could afford** to buy, his children **would be** very happy to greet a new year.
46. The kitchen will look better if we **have** red curtains.
47. If I knew his address, I **would go** round and see him.
48. If you **were not** so busy, I **would show** you how to play.
49. It **will be** quicker if you **use** a computer.
50. If we **have** some eggs, I **will make** you a cake.
51. Bring him another if he **does not like** this one.
52. She **will be** angry if she **hears** this tomorrow.
53. Unless you are more careful, you **will have** an accident.
54. If you **like**, I **will get** you a job in this company.
55. If grandmother **were** 5 years younger, she **would play** some games.
56. If the sun **stops** shining, there **will be** no light on earth.