Approach by sorting each method into its recovery category:
Instead of checking every option against a definition one at a time, it helps to first build a simple mental table of the three recovery stages and then place each of the four listed methods into its correct box.
Primary and secondary recovery box:
This box holds methods that rely on natural reservoir energy or on simple fluid injection purely to keep reservoir pressure up and physically displace oil, without changing the oil's own properties. Water flooding belongs squarely in this box, since injected water displaces oil mechanically but does not thin it out or reduce the capillary forces trapping it in the pore throats.
Thermal EOR box:
This box holds methods that add heat to the reservoir to reduce oil viscosity and improve its mobility. Steam flooding, where continuous steam injection heats the oil bank ahead of it, belongs here. In situ combustion also belongs here, since burning a portion of the oil downhole generates heat in place, achieving a similar viscosity reduction along with extra gas drive from the combustion products.
Chemical EOR box:
This box holds methods that use injected chemicals to alter interfacial properties between the oil, water, and rock. Surfactant flooding belongs here, since the surfactant molecules lower the oil water interfacial tension so that capillary trapped oil droplets can coalesce and move.
Reading off the answer from the sorted table:
Once every option is placed in its box, only water flooding lands in the secondary recovery box, while in situ combustion and steam flooding land in the thermal EOR box and surfactant flooding lands in the chemical EOR box. Since the question asks specifically for conventional EOR methods, the secondary recovery entry is excluded and the three EOR box entries are selected.
Final Answer:
\[ \boxed{\text{In situ combustion, Surfactant flooding, and Steam flooding}} \]