What Time Is It on the Moon? Scientists Consider How Lunar Clocks Could Work

Study the questions and tasks

Work through the material below, or start the interactive practice above to complete an attempt. Try the exercises before opening any answer or transcript sections, then use them to review your work.

Practice level

C1. Try this level if you can follow the instructions and understand most of the language; choose an earlier level if you need more support.

Question formats

Fill in the blank (dropdown)

How to approach this practice

Read the complete sentence and notice the subject, verb form, time reference and word order before answering.

1. Question 1 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   The proposed standard must ___ precise enough for navigation.

   Choices for blank 1

   1. be
   2. to be
   3. being
   4. been
   Check answers and explanations

   Blank 1

   be

   After modal “must,” use the bare infinitive “be.”

2. Question 2 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   Had organizations agreed on a common standard, they ___ fewer coordination problems.

   Choices for blank 1

   1. would have had
   2. will have
   3. would have
   4. had
   Check answers and explanations

   Blank 1

   would have had

   This mixed conditional requires “would have had” for the past result.

3. Question 3 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   The system was designed ___ information clearly across different platforms.

   Choices for blank 1

   1. communicating
   2. communicate
   3. to communicate
   4. communicated
   Check answers and explanations

   Blank 1

   to communicate

   The passive construction “was designed to” requires a to-infinitive.

4. Question 4 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   The more precisely clocks are synchronized, the ___ coordination becomes.

   Choices for blank 1

   1. smooth
   2. smoother
   3. smoothest
   4. smoothly
   Check answers and explanations

   Blank 1

   smoother

   The correlative comparative requires the comparative adjective “smooth.”

5. Question 5 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   The researchers recommended that the agencies ___ a shared protocol.

   Choices for blank 1

   1. establish
   2. established
   3. establishing
   4. to establish
   Check answers and explanations

   Blank 1

   establish

   After “recommended that,” formal English uses the mandative subjunctive “establish.”

6. Question 6 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   ___ the technical challenges, the project remains feasible.

   Choices for blank 1

   1. Despite
   2. Although
   3. Because
   4. While
   Check answers and explanations

   Blank 1

   Despite

   “Despite” must be followed by a noun phrase, not a finite clause.

7. Question 7 · Fill in the blank (dropdown)

   Choose the correct option for each blank.

   The instruments, ___ operate under different conditions, require compatible standards.

   Choices for blank 1

   1. that
   2. what
   3. which
   4. where
   Check answers and explanations

   Blank 1

   which

   A nonrestrictive relative clause referring to instruments requires “which.”

What to review next

After checking an answer, explain the rule in your own words and write a new sentence using the same pattern. Revisit any rules you could not explain.

A focused practice result shows how you did on these tasks. Use several activities across skills to decide what to study next; one practice score does not certify an overall CEFR level.