Choose the correct option to make one complete sentence without using and, but or so.
The construction started on time. It was delayed due to the bad weather.
Topic: Synthesis — clause of contrast
Try it
Pick an option and check your answer. The full worked answer is below either way.
Answer
(a) Although the construction started on time, it was delayed due to the bad weather..
Here the relationship is CONTRAST — it started on time and YET it was delayed — so ALTHOUGH is correct.
Why the others fail, and each fails on LOGIC rather than grammar: (b) "Since" means BECAUSE, which claims that starting on time caused the delay — nonsense. (c) "so" makes the same false causal claim, and the instruction forbids "so" in any case. (d) "as well as" makes the two facts merely additional, losing the contrast, and is clumsy English.
Compare this with question 3 above: there the relationship was REASON and the answer was "because"; here it is CONTRAST and the answer is "although". Identifying the relationship correctly is the whole exercise.
Although the construction started on time, it was delayed due to the bad weather..