Here are the appropriate words to fill in the gaps:

41. My father works as **an** electrician.
42. It is cold because **the** heating systems are broken.
43. Did you buy **a** pair of shoes yesterday?
44. She took **a** hamburger and **some** apples, but she didn’t eat **any** apples.
45. James offered me **a** cup of coffee and **a** piece of cake. **The** cake is...
46. This is **a** unique custom of this ethnic group.
47. No one in my family likes drinking **much** beer.
48. It took me **an** hour to finish my homework.

For 42, "the" is not part of your instruction but fits in context.