A person who designs, maintains or builds machines.
        
                    
             
        
        
        
Answer: File History
Explanation: File history is the history that gets created in the form of back-up that keeps the record of the stored files. It is used in protecting the files  that is present on the system like desktop, libraries,etc.
It creates the duplicate records in the storage for any future use and it can also be restored easily.File history also facilitates with feature of deleting the unnecessary history afterward when the user wants.
 
        
             
        
        
        
The loop terminates when "xxxxx" is read in. If the word is land, the string followed by "land" get outputted. The same with air, and water.
Explanation:
int land = 0;
int air = 0;
int water = 0;
String word = "";
while(!(word.equals("xxxxx"))) {
 word = stdin.next();
if(word.equals("land")) {
    land++;
}else if(word.equals("air")) {
    air++;
}else if(word.equals("water")) {
    water++;
}  
}
System.out.println("land:" + land);
System.out.println("air:" + air);
System.out.println("water:" + water);
 
        
             
        
        
        
Answer:
light year
Explanation:
Its is equal to 9,500,000,000,000km