In 1990, California native and researcher Ellen Ochoa left her position as chief of the Intelligent Systems Technology Branch at...

Sentence Structure

• In 1990,
  • California native and researcher Ellen Ochoa
    • left her position
      • as chief of the Intelligent Systems Technology Branch
        • at a NASA research center
    • ____[?] the space agency's astronaut training program.

Understanding the Meaning

The sentence starts with a time marker:

• 'In 1990'
  • This sets the timeframe - we're talking about something that happened in the past.

Then we meet the subject:

• 'California native and researcher Ellen Ochoa'
  • This is who the sentence is about.

Now we learn what she did:

• 'left her position as chief of the Intelligent Systems Technology Branch at a NASA research center'
  • This is the main action - she left her job
  • The details tell us it was a pretty important position - she was the chief of a branch at NASA.

Now here's where we need to fill in the blank:

• 'left her position... ______ the space agency's astronaut training program'

Let's look at our choices:

• We need to decide between different verb forms: "to join," "is joining," "joined," or "joins"

Based on what we've read, the sentence is telling us that Ellen Ochoa left one position. Now we need to connect that to the astronaut training program. Let's think about the relationship:

• She left her position... for what reason?
• Why did she leave?

What do we notice about the structure here?

• We have a main action: "left her position"
• The next part needs to explain the PURPOSE - why she left
• When we want to express purpose (the reason for doing something), we use the infinitive form: to + verb
• It answers the question "Why did she leave?" → "to join the training program"

So we need "to join" - this expresses that she left her position FOR THE PURPOSE OF joining the astronaut training program.

The complete sentence tells us: In 1990, Ellen Ochoa left her important research position in order to join NASA's astronaut training program.

GRAMMAR CONCEPT APPLIED

Using Infinitives to Express Purpose

When you want to show WHY someone did something - the purpose or goal behind an action - you use an infinitive form (called an infinitive in grammar terms: "to" + base verb). The infinitive follows the main verb and explains the reason or intent.

Pattern:

• [Subject] + [main verb] + [infinitive showing purpose]

Examples:

• Example 1:
  • She went to the library to study for her exam
  • Main action: "went to the library"
  • Purpose (why?): "to study"
• Example 2:
  • The company hired a consultant to improve efficiency
  • Main action: "hired a consultant"
  • Purpose (why?): "to improve efficiency"
• In our question:
  • Ellen Ochoa left her position to join the astronaut training program
  • Main action: "left her position"
  • Purpose (why?): "to join the astronaut training program"

The infinitive "to join" tells us her goal or reason for leaving - she left that position SO THAT she could join the training program.