Please if you know this one answer quickly and check out the other question as well.
You need to change the toString in Cog to also return the data in the variable value in Thing. Which of the following would correctly do this?

public String toString() {
return "" + toString() + " " + num;
}

public String toString() {
return "" + value + " " + num;
}

public String toString() {
return "" + super. value + " " + num;
}

public String toString() {
System. out. println("" + value + " " + num);
}

public String toString() {
return "" + super. toString() + " " + num;
}