Final answer:
To form a complex sentence from 'The car was stuck in the snow,' we can add a subordinating conjunction such as 'because,' resulting in 'The car was stuck in the snow because a severe blizzard had swept through the night.' This provides a cause for the car being stuck.
Step-by-step explanation:
The question involves constructing a complex sentence by adding a subordinating conjunction to an existing sentence. To create a complex sentence, we need to attach a subordinate clause to the main clause. Here is an example using the subordinating conjunction 'because':
'The car was stuck in the snow because a severe blizzard had swept through the night.'
In this example sentence, 'because' introduces the subordinate clause 'a severe blizzard had swept through the night,' which provides the reason why the car was stuck in the snow. By using a subordinating conjunction to join these two clauses, the sentence effectively communicates a cause-and-effect relationship.