Doldrum  is  the     region  of   very   calm  and  little or  no  wind  on  either side   of  the  equator. Doldrums  which  is  also  called  convergence  zone  is   an  equatorial  region  of  the  Atlantic  ocean  which  has  sudden  storms   and  light  unppredictable  winds.  In  addition  doldrum  is  abelt  around  the   earth  near   the  equator  where  the   sailing  ships  sometimes get  stuck  on  windless  water.
        
             
        
        
        
Answer:
The greater the amount of silica in magma, the more viscous the magma is. The magma thus solidifies quicker as well.
 
        
             
        
        
        
Answer: United States, Canada, and Mexico
Explanation:
 
        
                    
             
        
        
        
Answer:
"All of them except last one."
Explanation:
All of the given options represent NASA future projects:
- Use a probe to collect data- Parker Solar Probe will be the first-ever mission to study the Sun from such a small distance. The spacecraft will travel directly into the Sun's atmosphere about 4 million miles from the surface.
- Improve aviation technology- NASA is currently working on the development of the new experimental aircraft X-plane which will prove the dramatic benefits of advanced technologies in piloted flight.
- Conduct research from a space station- Humans are already living and working on board of the International Space Station which is one-of-a-kind research laboratory in micro gravity. A portion of the astronauts time aboard the space station has been designated for national laboratory investigations.
- Collect samples on an asteroid- First asteroid sample return mission, OSIRIS-R Ex, arrives at the near-Earth asteroid Bennu in December 2018 and should return a sample for study in 2023.
- Conduct an unmanned space mission- In Sight Mars lander is set to study the planet’s interior. The Mars 2020 rover will search for signs of past microbial life, gather samples for future return to Earth and investigate resources. The James Webb Space Telescope will be the premier observatory of the next decade, studying every phase in the history of our Universe in infrared