Word Jumble that doesn't choose the same word?

[KitkatEmmKay]

Hello i'm new to C++ and i'm a student studying game art & design taking a basic C++ class this quarter. Recently my professor gave us word jumble game assignment and i'm having a hard time trying to figure out how to get my code to NOT choose the same word. I just want it to choose each word one by one randomly and then after it's chosen that word to ignore it from that point on. right now this is what i have in my source.cpp

  #include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
using namespace std;

int main()
{
	enum fields { WORD, HINT, NUM_FIELDS };
	const int NUM_WORDS = 10;
	const string WORDS[NUM_WORDS][NUM_FIELDS] =
	{
		{ "Earth", "What we live on, we what should take care of." },
		{ "Nature", "It surrounds us, it's part of us." },
		{ "Celebrate", "champagne anyone?" },
		{ "Trees", "tall, made of wood, duh?." },
		{ "EarthDay", "The day this game's about!." }

	};
	Newword:
	srand(static_cast<unsigned int>(time(0)));
	int choice = (rand() % NUM_WORDS);
	string theWord = WORDS[choice][WORD]; // word to guess
	string theHint = WORDS[choice][HINT]; // hint for word
	string jumble = theWord; // jumbled version of word
	int length = jumble.size();
	for (int i = 0; i < length; ++i)
	{
		int index1 = (rand() % length);
		int index2 = (rand() % length);
		char temp = jumble[index1];
		jumble[index1] = jumble[index2];
		jumble[index2] = temp;
	}
	cout << "\t\t\tWelcome to Word Jumble!\n\n";
	cout << "Unscramble the letters to make a word.\n";
	cout << "Enter ’hint’ for a hint.\n";
	cout << "Enter ’quit’ to quit the game.\n\n";
	cout << "The jumble is: " << jumble << endl;
	string guess;
	cout << "\n\nYour guess: ";
	cin >> guess;
	while ((guess != theWord) && (guess != "quit"))
	{
		if (guess == "hint")
		{
			cout << theHint;
		}
		else
		{
			cout << "Sorry, that’s not it.";
		}
		cout << "\n\nYour guess: ";
		cin >> guess;
	}
	if (guess == theWord)
	{
		cout << "\nThat’s it! You guessed it!\n";
		goto Newword;
	}
	cout << "\nThanks for playing.\n";


	system("pause");
	return 0;
}
	

if someone could possibly point out what i'm doing wrong or what i'm missing i'd be very much appreciative!

[Gamer2015]

put srand over the Newword block.

And please, I beg of you, don't use goto, use a loop instead.