A material BOM is a list of components that make up a material. It can be used to describe the structure and composition of a product or a spare part. A material BOM can be assigned to one or more technical objects, such as equipment or functional locations, to define the materials required for maintenance activities1.
One way to assign a material BOM to a piece of equipment is via the field construction type in the equipment master. The construction type is a material number that identifies the material BOM for the equipment. By entering the construction type in the equipment master, the system automatically assigns the material BOM to the equipment2.
The other options are incorrect because:
Via field model number in the equipment master: The model number is a material number that identifies the material of the equipment itself, not the material BOM. It is used to create an equipment BOM, which is a list of components that are installed on the equipment. An equipment BOM can be different from a material BOM, as it can reflect the actual configuration of the equipment2.
Via material BOM header in the serialization data: The serialization data is a view in the material master that contains information about the serial numbers of the material. It is not related to the material BOM or the equipment assignment3.
Via creation of an equipment BOM: The creation of an equipment BOM is a different process from the assignment of a material BOM. An equipment BOM can be created from a material BOM, but it does not automatically assign the material BOM to the equipment. An equipment BOM can also be created manually or copied from another equipment2.
References: 1: Using Bills of Materials (BOMs) - SAP Learning 2: SAP PM Bills of Material Tutorial - Free SAP PM Training - ERProof 3: Serialization Data (SAP Library - Material Master (LO-MD-MM))

Explanation
To display vehicle-specific data for a piece of equipment, such as the vehicle type, the vehicle class, the registration number, the license plate, and the vehicle identification number, you need to assign a view profile to an equipment category for fleet equipment. A view profile defines which fields are displayed and editable for a specific equipment category. You can create and assign view profiles in Customizing for Plant Maintenance and Customer Service under Master Data in Plant Maintenance and Customer Service -> Technical Objects -> Equipment -> Define View Profiles for Equipment Categories. You can also assign a view profile to an equipment category for fleet equipment in Customizing for Plant Maintenance and Customer Service under Master Data in Plant Maintenance and Customer Service -> Technical Objects -> Fleet Management -> Assign View Profiles toEquipment Categories for Fleet Equipment1. References: 1:
SAP Help Portal, SAP S/4HANA Asset Management, Learning Journey: SAP S/4HANA Asset Management, Topic: Fleet Management, Subtopic: Vehicle-Specific Data for Equipment.