[单项选择]预算定额中的人工幅度差主要是指（）。
A. 预算定额人工工日消耗量与施工定额中的劳动定额消耗量之差
B. 预算定额人工工日消耗量与概算定额消耗量之差
C. 预算定额人工工日消耗量测定带来的误差
D. 预算定额人工工日消耗量与其净消耗量之差

{{B}}Trade Unions{{/B}}
1．Some scholars have associated trade unions with the medieval craft guilds(中世纪的行会), but there are important differences between the two. The guild members were master craftsmen who owned capital and often employed workers. Unions are known as associations of workers with similar skills.
2．In the past, individual workers had no control over the conditions of their working lives; political and economic power was concentrated in the hands of wealthy business owners. Workers found, however, that there was strength in uniting. From their earliest years, union objectives have been higher wages and improved working conditions.
3．Employers resisted, of course. They made great efforts to stop union organizing its activities. Union members were fired, workers were forced to sign contracts in wh