Echo Array cell value is not complete

Array for the

Array ([title] = The top of the book Math Quiz [ID] + 6 [subject] [[Parts] = [["Radio", "1]" [[]] [topic] =    [["1", "100"]] [JSON] = [["6", "
Little Red does a math problem "
  
   '; Color:rgb (0,0,0); font-weight:bold;font-size:14px;font-family: [#39; ' > Two polynomial
   
    ' Font-family:times New Roman ' >a
    ,
    B
    ,
    B
    to be
    , try 
      
       ' font-family:times New Roman ' >a B
       
    the value
    ". Little Red mistakenly will 
      
       ' font-family:times New Roman ' >a B
       
    considered
    A
    -
    
     
      '; Color:rgb (0,0,0); font-size:14px;font-family: [#39; ' >b 
      
       ' font-family: Song body, the result answer (calculated correctly) is 
       .  
      

     
    
   
  
 
  
   ' text-indent:21px;line-height:200% ' > 
   ( 
    
     ' font-family:times New Roman ' >2 
      
   ) Find out when 
    x 
   
     '; Color:rgb (0,0,0); font-size:14px;font-family: [#39; ' ] = 3 
    at 
    the value of 
    a B 
    .
  
  
  
  
    

  
    

", 1," [
    
 
 
 

   +]] [total] = +)
 

I'm printing the JSON keys, but I'm not printing them all, showing

[["6", "