Question

Roberts already (finished, had finished) the experiments by the time Fuller made the discovery in his own laboratory.

Short answer

The correct answer is 'had finished'. The sentence should be 'Roberts had finished the experiments by the time Fuller made the discovery in his own laboratory'.

Step-by-step solution

Understanding the Sentence Structure

First, read and understand the sentence. Note that 'Roberts' completed the experiments and 'Fuller' made the discovery - these are two discrete events.

Understanding the Time Frame

In this sentence, there is a specific time framing clause, 'by the time Fuller made the discovery in his own laboratory'. This clause indicates that one event (Roberts completing the experiments) happened before another event (Fuller's discovery). The keyword 'by the time' often indicates the need for past perfect tense to show the sequence of the events.

Choosing the Correct Tense

Given that the completion of experiments by Roberts happened before Fuller's discovery, the action needs to be in past perfect tense. So, the use of 'had finished' is the appropriate choice to indicate this sequence.

Key concepts

Sentence Structure

When writing sentences, it is important to consider how different parts are organized to convey the intended meaning. Sentence structure involves the arrangement of words and phrases to create well-formed sentences. In the context of the exercise, understanding who performed each action and the order of these actions is crucial. The sentence contains two main actions: 'Roberts finished the experiments' and 'Fuller made a discovery'. These actions are attributed to two subjects, 'Roberts' and 'Fuller', which makes it easier to track what happened and who did it.
Breaking down such a sentence involves identifying:

• The subjects: 'Roberts' and 'Fuller'
• The verbs: 'finished' and 'made'
• The objects or results of these actions

The sentence must clearly define these elements to ensure clarity. This structure helps in understanding how these events are linked, particularly when showing which happened first.

Time Framing Clause

A time framing clause is a part of the sentence that provides context about when certain events occurred. In the given exercise, the clause "by the time Fuller made the discovery in his own laboratory" serves this purpose. It provides a temporal frame to the sequence of events, helping readers understand when each action took place.
A few characteristics of time framing clauses include:

• They often begin with words like 'by the time', 'when', 'after', which signal the timing of one event in relation to another.
• They act as a marker to show the relationship between two distinct events.

In the sentence from the exercise, the phrase "by the time" suggests that Robers' event (completing experiments) was completed before the second event (Fuller's discovery) took place. This understanding is vital for choosing the correct tense.

Sequence of Events

The sequence of events provides a timeline for when actions occur in relation to each other. In the exercise at hand, understanding this sequence is critical for applying the correct verb tense. The sentence indicates that Roberts' action happened before Fuller's, hence the sequence is such that Roberts concluded his experiments prior to Fuller's arrival at a discovery.
To properly convey such a sequence, the past perfect tense is employed. This tense is used to talk about actions that were completed before another action in the past:

• Past perfect involves the structure 'had' + [past participle] (e.g., 'had finished').
• It clearly distinguishes the order of past events, which helps avoid ambiguity.

In this exercise, 'had finished' indicates that the experiments were completed beforehand, establishing the correct sequence and offering clarity to the reader on the timeline of events.