The new road was completed on schedule … the difficulties involved.

Analyze the question The sentence is: "The new road was completed on schedule __ the difficulties involved." The blank is followed by a noun phrase ("the difficulties involved"), not a full clause. So we need a word that introduces a noun phrase and shows contrast.

Explain the concept

• Although is a conjunction. It must be followed by a clause (subject + verb), e.g. "Although there were difficulties..."
• Despite (and in spite of) is a preposition. It is followed by a noun or noun phrase, e.g. "despite the rain".
• Besides means "in addition to" and adds information. It does not show contrast.
• However is an adverb or connector. It usually starts a new sentence or clause, e.g. "However, the road was completed..." It cannot join a sentence to a noun phrase like this.

Solution

1. The blank is followed by "the difficulties involved", which is a noun phrase.
2. The meaning is contrast: the road was finished on time even though there were difficulties.
3. Only a preposition of contrast fits both the grammar and the meaning, and that is despite.

Completed sentence: "The new road was completed on schedule despite the difficulties involved."

Answer: B. despite

Tip: Remember the pairing:

• Although / though / even though + clause (subject + verb)
• Despite / in spite of + noun or -ing form

Note that "despite of" is never correct. Use "despite" alone, or "in spite of".