Answer:
The correct answer choice is B
Explanation:
We use these brackets in the first place to show the main molecule interconnection with other appendage molecules. For example, Ca(OH)2. The main molecule of calcium is joined with other two molecules and  brackets are showing interconnection simply. However, these brackets can't tell us about the orientation and position of bond in 3D space. We have to utilize stereo-chemistry for that...
 
        
             
        
        
        
Answer:
Xe
Explanation:
Cs and Na are solids in room temperature while F and Xe are gases.
The number of electrons in the outermost shell of an atom will determine its reactivity. Out of the gases given Xe and F, F ( the most electronegative element) posses 5 valence shell electrons which makes it highly reactive while Xe which is a noble gas posses 8 valence shell electrons which makes it less reactive compared to many elements.
 
        
             
        
        
        
Hello!
If you look at a zipper, you'll see that it doesn't have a wheel or an axle. A zipper links the <span>protruding teeth that the zip contains. Your answer would be B!
You can feel free to let me know if you have any questions regarding this!
Thanks!
- TetraFish</span>