Grumbs as a Bingo $\Rightarrow$ Ihavitoo must also be present (rule 3).
Since the 2 Bingoes are Grumbs and Harrumphs, Ihavitoo cannot be a Bingo — it must then be the Cingo to satisfy the “Ihavitoo present” requirement. Thus, I is true.
Dingoes = 2 required. They can be from \{Lovitoo, Metoo, Nana\}. No rule forces Lovitoo to be chosen unless Koolodo appears (which is not mentioned here). Hence II is not necessarily true.
However, Lovitoo or Metoo must appear because we need 2 Dingoes, and without either of them, we would have Nana and one more — possible. Actually, rule says nothing about requiring Lovitoo/Metoo — so III must be rechecked: Without Lovitoo and Metoo, both Dingoes would be Nana repeated, which is not stated as allowed — so in normal unique-word assumption, we must pick at least one of Lovitoo/Metoo. Hence III is true.
Thus, I and III are true.
\(\boxed{\text{Correct Answer: (D) I & III only}}\)