Step 1: Understand the context of the question
The question is asking about a type of foreign exchange (forex) transaction that is conducted based on standardized principles.

Step 2: Identify the key characteristics of the transaction
The key characteristic mentioned is that the transaction is conducted according to 标准化原则 which translates to standardized principles.

Step 3: Relate the characteristic to types of forex transactions
In the context of forex, transactions can be categorized into different types based on their characteristics, such as spot transactions, forward transactions, swaps, and futures、The mention of 标准化原则 suggests a transaction type that is highly regulated and standardized.

Step 4: Recognize the type of forex transaction that fits the description
Forex futures are a type of transaction that is traded on an exchange and is subject to standardized principles, including contract sizes and expiration dates.

Step 5: Conclude the type of forex transaction
Given that forex futures are traded on exchanges and are subject to standardized rules, this matches the description provided.

The best answer is C.