1 . The fact that space exploration has increassed threatically in the past three years_. 

• A. is an evidence of us wanting to know mare of our solar systems
• B. how we want to learn more about the solar systems
• C. is pointing to evidences of our intention to know a lot more about what is called our solar systmes
• D. indicates that we are very eager to learn all we can about our solar systems

Answer: Option D

Explanation: