63. The only way you can become a good athlete is to train hard
every day.
→Only by

62. Galileo is considered to be the father of modern astronomy.
→Galileo 

61. The only reason the party was a success was that a famous film
star attended.
→Had 

60. Although Nam was the stronger of the two, his attacker soon
overpowered him.
→Despite 

59. Immediately after his arrival, things went wrong.
→No sooner 

58. You might fall if you are not careful.
→Be 

57. We should ban the use of pesticides, but we should also restrict
the use of other chemicals.
→In addition to

56. We must do something about the problem even if it costs a lot.
→Costly 

55. May I borrow your pen?
→Would

54. Why isn’t this TV working?

what.....