Help me please i need help

Plz plz plz quick! 49 points for whoever which of the following statements about greenhouse effect is true? *life on earth is suffering because of greenhouse effect *the greenhouse effect is caused by human activity *all greenhouse gases are harmful *life on earth would not exist without the greenhouse effect

What are some possible short and long term medical concerns for crew members on longer space exploration trips

For a comparative or experimental investigation, scientists often make a testable about a scientific question, and then they test it in the investigation. a.control b.hypothesis c.procedure d.system