Explanation:

The Seventh Schedule of the Indian Constitution divides legislative authority between the Union and State governments through three lists: the Union List, the State List, and the Concurrent List. Analyzing the items given:

"Officers and servants of the High Court" - This falls under the State List. The organization, jurisdiction, and terms of employment of the officers and servants of the High Courts are typically under the purview of the State Government.

"Gas and gas-works" - This is also under the State List. The states have the authority to legislate on matters concerning the production, supply, and distribution of gas and the construction and operation of gas-works.

"Betting and gambling" - This is part of the State List as well. States have the exclusive right to legislate on betting and gambling.

Therefore, all three items listed fall under the State List in the Seventh Schedule of the Indian Constitution.