Sugar or A sugar

[Freeguy]

The basic source or calories is glucose, ...... produced by plants.

1. a sugar
2. sugar
3. is a sugar
4. which it is a sugar

In my opinion No.2 is correct. However the answer key says it must be No.1. Don't we use sugar as an uncountable noun in this sense?

 

[Raymott]

The basic source or calories is glucose, ...... produced by plants.

1. a sugar
2. sugar
3. is a sugar
4. which it is a sugar

In my opinion No.2 is correct. However the answer key says it must be No.1. Don't we use sugar as an uncountable noun in this sense?

Not in this sense, no. Glucose is a sugar. But table sugar is sucrose. It would be misleading to leave out the ''a'. Besides there are other sugars produced by plants, eg. fructose. So glucose is only one sugar which is produced by plants - hence, "a sugar".

[Not a botanist]

 

[MikeNewYork]

The basic source or calories is glucose, ...... produced by plants.

1. a sugar
2. sugar
3. is a sugar
4. which it is a sugar

In my opinion No.2 is correct. However the answer key says it must be No.1. Don't we use sugar as an uncountable noun in this sense?

Either 1 or 2 is correct, grammatically. Sugar can be countable or uncountable. However, plants produce sugars other than glucose, so #1 is the correct answer scientifically.

 

[5jj]

The basic source or calories is glucose,

... source of calories ...