Final answer:
The sentence 'The road builders were blocked by rivers and canyons' can be combined by using a subordinating conjunction such as 'although' or 'despite'.
Step-by-step explanation:
The sentence 'The road builders were blocked by rivers and canyons' can be combined by using a subordinating conjunction such as 'although' or 'despite'. We can rephrase it as:
Despite being blocked by rivers and canyons, the road builders persevered.
Learn more about Combining sentences