Hint: One-party system means a system in which only one party operates in the political system for various reasons.
Complete answer: Similar to every other traditional socialist political system, in the Chinese political system also the Communist Party of China(CPC) was a dominant position as the custodian of world power. The Constitution of 1982 does not assign a place to it and its text involves a separation between the party and the state administration, yet by virtue of being the single largest party with a glorious record of the key role in the pre and post-revolutionary eras, the Communist Party of China continues to play a big, active and dominant role in the working of Chinese political system. Several other minor political parties do exist in China but all these exist because of its friendly relationship with the Communist Party and because they are willingly playing a second fiddle in politics by acting in accordance with the dictates of Communist Party. Hence, the Chinese political system has been living with a single-party system with the Communist Party of China acting as the vanguard of the people and the real power holder of the state. Now let us examine the options:
Option A - China from the very beginning had a one-party system. Communist Party of China (CCP) enjoys a dominant position even though several minor political parties do exist in China. These minority parties do not have much say in the functioning of the government.
Option B - Indo-China consists of 6 countries - Cambodia, Laos, Myanmar, Malaysia, Thailand and Vietnam; of which only Laos and Vietnam have a one-party system.
Option C - Japan earlier had a one-party system but now it follows the framework of a multi-party system.
Option D - Germany has a plural multi-party system.
Thus, the correct answer is option (A).
Note: The role of the Communist Party in the Chinese political system has been, continues to be, and is destined to continue in future as a formidable role as the core of leadership and vanguard of the people in the struggle to develop further in accordance with the socialist objectives that stand accepted by the principle of collective leadership in the post-Mao period.