DSE English Grammar: Clauses

詳解：A defining relative clause identifies the noun it modifies and is essential to the meaning. In B, 'that I borrowed from the library' specifies which book. The other options use non-defining clauses (set off by commas) that add extra information.

詳解：After 'the reason', we use 'why' to introduce a clause explaining the reason. 'Which' and 'that' are possible in some contexts but 'why' is most natural here. 'What' is incorrect; we don't say 'the reason what'.

詳解：The clause 'if he will come' functions as the object of the verb 'wonder', making it a noun clause. It is not an adverbial clause because it does not modify the verb or express condition/time in that way.

詳解：A non-defining relative clause adds extra information and is set off by commas. In C, 'who is a nurse' is non-essential and correctly placed between commas. The other sentences use defining clauses (no commas) that are essential to identify the noun.

詳解：'Even though' introduces a contrast clause meaning 'in spite of the fact that'. 'Despite' is a preposition, not a conjunction, and would require 'the fact that'. 'Because' gives a reason, and 'unless' introduces a condition, neither fits the meaning.

詳解：A reduced relative clause omits the relative pronoun and the verb 'be'. In B, 'sitting there' replaces 'who is sitting there'. Option A is the full form, C uses a defining clause, and D is non-defining.

詳解：'So that' introduces a clause of purpose, indicating the intention behind an action. 'In case' is for precaution, 'as long as' for condition, and 'even if' for concession. The sentence expresses purpose, so 'so that' is correct.

詳解：In B, the clause 'That he is honest' acts as the subject of the sentence. In A, the noun clause is the object of 'know'. In C, 'the fact that...' is a noun phrase with an appositive clause. In D, 'which is known' is a relative clause.

詳解：'Which' is used for things, not people. For a person, we use 'who' (subject) or 'whom' (object). Here, 'the woman' is the object of 'met', so 'whom' is correct, though 'who' is often used informally. 'That' can also refer to people but 'which' is wrong.

詳解：Option B uses a participial phrase ('causing widespread damage') to correctly combine the sentences, showing cause and effect. A is ungrammatical ('so causing' is not standard). C is awkward (parallel structure issue). D is a comma splice (two independent clauses joined only by a comma).