A、two weeks. B、a month. C、an unknown period. D、three days. C新闻提到，农民联合会表示罢工还将持续多久仍未可知，可见C为正确答案。unknown period是undetermined period

Farmers and their supporters protested Wednesday in hundreds of rural locations in Argentina on the two-week mark of the farmers’ strike against an increase in export taxes for their products. Women in Cordoba, Argentina, bang pots in support of the farmers’ strike on Wednesday. In some places, protesters blocked roads to the capital. On those roads, the farmers have stopped trucks transporting food and other farm-related products, Other vehicles were allowed to pass.The farmers’ federations have said that the strike will continue for an undetermined period of time. The strike’s impact already is visible on the nearly empty supermarket shelves in cities. Butchers and supermarkets were among the first hit.The noise of Tuesday’s caeerolazos evoked memories of the protests in 2001 that forced then-president Fernando de la Rua from power.