The methods used to extract metals in the middle of the activity series are _____

1. Reduction of metal oxides with carbon  
2. Reduction of metal oxides with carbon monoxide 
3. Auto reduction 
4. Reduction of ore by more reactive metal

Metals such as iron, zinc, lead, copper, etc., are considered to be in the middle of the activity series. These metals have a moderate reactivity and are usually found in nature as sulphides or carbonates. The extraction of these metals from their ores is typically achieved through reduction processes.

Reduction involves converting metal oxides into their respective metals. The most common method for reducing metal oxides is by using carbon, which is capable of reducing many metal oxides to produce the metal and carbon dioxide. This method is particularly effective for metals like iron and zinc.

Another method of reduction involves the use of carbon monoxide. Carbon monoxide is a strong reducing agent and can also reduce metal oxides. This method is commonly used for extracting metals like lead, copper, and others, where carbon monoxide serves as a reducing agent to extract the metal from its ore.

In some cases, auto-reduction occurs, where a metal is reduced by its own elements, typically when the ore is heated. This happens in certain processes where the metal oxide undergoes a spontaneous reduction without needing an external reducing agent.

Additionally, the reduction of ore by a more reactive metal is another method used for extracting metals in this range. A more reactive metal can displace the metal of interest from its ore, resulting in the extraction of the desired metal.