Question 109·Easy·Boundaries
Onboard the International Space Station, astronauts follow a strict exercise routine ______ about two hours each day to counteract the effects of microgravity on muscle and bone density.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation-boundary questions, first read the sentence without looking at the choices and listen for natural pauses. Identify whether the words around the blank form one continuous phrase, start a new clause, or introduce a list or explanation. Then recall what each punctuation mark signals (comma = light pause/extra info, colon = follows a complete sentence to introduce something, dash = strong break or interruption) and choose the option that matches the sentence structure and meaning while keeping the grammar standard and the flow smooth.
Hints
Check how the sentence sounds
Read the sentence aloud in your head. Does it feel like you naturally pause before the words "about two hours each day," or do those words flow directly as part of the description of the exercise routine?
Decide what comes after the blank
Look closely at the words that follow the blank: "about two hours each day." Are these words starting a new idea or list, or are they just continuing to describe the exercise routine?
Match the punctuation to its job
Think about what a colon, a comma, and a dash usually do in a sentence. Ask yourself: would it make sense here to signal a list, a big pause, or an interruption right after the word that goes in the blank?
Step-by-step Explanation
Read the sentence smoothly without focusing on the blank
Read the full sentence and imagine the blank is already filled by a normal word:
"Onboard the International Space Station, astronauts follow a strict exercise routine ___ about two hours each day to counteract the effects of microgravity on muscle and bone density."
Ask yourself: does it sound like there should be a pause or break before "about two hours each day," or should the description flow smoothly?
Identify the role of the words after the blank
The words "about two hours each day" tell how long the exercise routine lasts.
Together, "lasting about two hours each day" forms a single descriptive phrase (a modifier) that describes "exercise routine." It is not a separate sentence and does not show a big shift in thought; it simply continues the description of the routine.
Recall what colons, commas, and dashes do
Each punctuation mark in the options signals a break in the sentence:
- A colon usually comes after a complete sentence to introduce an explanation, list, or example.
- A comma here would signal a light pause, often setting off nonessential or extra information.
- A dash signals a strong break or interruption in thought.
Here, "lasting about two hours each day" is tightly connected to "exercise routine" and is not extra or separate information, so inserting a break right before "about" would be unnatural and grammatically weak.
Choose the version that keeps the phrase together
Because the description "lasting about two hours each day" should flow directly after "exercise routine" without any interruption, the correct choice is the one that uses no punctuation between "lasting" and "about": D) lasting.