The numeral for ninety million ninety thousand ninety is
a)9090095
b)90090090
c)909090
d)None of these

Hint: In this question, we need to find the expression of a number given in words in its decimal representation. Also, the given number is stated in the international system of numeration, therefore, we should try to understand the international system of numeration and use it to obtain the answer to this question.

Complete step-by-step answer:
In the international system of numeration, the values of the places from the right to left (before the decimal place) are one, ten, hundred, thousand, ten-thousand, hundred thousand, millions, ten million, hundred million and so on. Thus, commas are put after every three places from the right.
The given number is ninety million ninety thousand ninety. Thus, in this case there should be 0 at the one’s place, 9 at the ten’s place, 0 at the hundred’s place, 0 at the thousand’s place, 9 at the ten-thousand’s place, 0 at the hundred-thousand’s place, 0 at the one-million’s place and 9 at the ten-million’s place.
Thus, the number corresponding to ninety million ninety thousand ninety should be 90,090,090 which matches option (b). Thus, option (b) is the correct answer to this question.

Note: We should be careful that in the international system of nomenclature each triplet which are put in commas can be considered as one-x, hundred-x and thousand-x for a given variable x (for example x can be written as million, billion, trillion etc.) and thus, the appropriate answer should have zeros at the appropriate places according to this rule.