The sentences below have words that are missing. Choose the best option from those given below to complete the sentence.
Achieving spaceflight enabled humans to begin to explore the solar system and the rest of the _________, to understand the many objects and____________ that are better observed from a space perspective, and to use for human benefit the resources and attributes of the space environment. All of these activities - discovery, scientific understanding, and the __________ of that understanding to serve human purposes - are elements of space __________.

We can fill in the given triplets in the sentence and interpret them to find the one that best conveys the meaning:

• A. Achieving spaceflight enabled humans to begin to explore the solar system and the rest of the galaxy, to understand the many objects and ideologies that are better observed from a space perspective, and to use for human benefit the resources and attributes of the space environment. All of these activities - discovery, scientific understanding, and the enormity of that understanding to serve human purposes - are elements of space visualisation.
  "Ideologies" is unrelated to physical or scientific objects, and "enormity" is incorrectly used; it refers to something morally wrong or immense in a negative sense.
• B. Achieving spaceflight enabled humans to begin to explore the solar system and the rest of the universe, to understand the many objects and phenomena that are better observed from a space perspective, and to use for human benefit the resources and attributes of the space environment. All of these activities - discovery, scientific understanding, and the application of that understanding to serve human purposes - are elements of space exploration.
   All four words—universe, phenomena, application, and exploration—are scientifically accurate and clearly relate to the context of space study and usage. 
• C. Achieving spaceflight enabled humans to begin to explore the solar system and the rest of the cosmos, to understand the many objects and materials that are better observed from a space perspective, and to use for human benefit the resources and attributes of the space environment. All of these activities - discovery, scientific understanding, and the principles of that understanding to serve human purposes - are elements of space identification.
   While cosmos and materials fit fairly well, principles is not something one can "serve" with, and identification does not capture the broader goal of space activity like exploration does. 
• D. Achieving spaceflight enabled humans to begin to explore the solar system and the rest of the configuration, to understand the many objects and elements that are better observed from a space perspective, and to use for human benefit the resources and attributes of the space environment. All of these activities - discovery, scientific understanding, and the functioning of that understanding to serve human purposes - are elements of space vastness.
  Configuration and functioning are vague and awkward here. Vastness refers to size, not a process or set of activities.

Out of the four options, option B fits the context best. 'Universe' accurately reflects the scope of space exploration. 'Phenomena' are observable events or occurrences in space. 'Application' correctly refers to using scientific knowledge for human benefit, and 'exploration' ties all the ideas together under the umbrella of space activity.

Correct answer: B