Which of the following is classified as an explicit trading cost?

Broker commission is classified as an explicit trading cost because it is a direct and identifiable fee paid to a broker for executing trades on behalf of an investor. This cost is known in advance and can be clearly outlined in the transaction details. Explicit trading costs are those that are directly charged and readily ascertainable, making broker commissions a textbook example.

In contrast, bid/ask spread represents a cost associated with the difference between the buying price and selling price of a security, which might not be easily quantified upfront. Market impact refers to the effect that a trader's order has on the market price of a security, and while it can often be measured, it is more of an implicit cost as it isn't a direct fee paid. Delay costs arise when a trader cannot execute a trade immediately, potentially leading to unfavorable price changes, which also falls into the category of implicit costs. Thus, broker commissions stand out as the clear example of an explicit trading cost.