Read the passage and then answer the following question: which of the statements listed after the passage is true?

one of the first strikes of cotton-factory operatives that ever took place in this country was that in lowell, in october, 1836. when it was announced that the wages were to be cut down, great indignation was felt, and it was decided to strike, en masse. this was done. the mills were shut down, and the girls went in procession from their several corporations to the "grove" on chapel hill, and listened to "incendiary" speeches from some early labor reformers.

one of the girls stood on a pump, and gave vent to the feelings of her companions in a neat speech, declaring that it was their duty to resist all attempts at cutting down the wages. this was the first time a woman had spoken in public in lowell, and the event caused surprise and consternation among her audience. .

it is hardly necessary to say that so far as results were concerned this strike did no good. the dissatisfaction of the operatives subsided, or burned itself out, and though the authorities did not accede to their demands, the majority returned to their work, and the corporation went on cutting down the wages.

a.
there was a causal relationship between the lowell workers' anger and the mills being shut down.

b.
there was a causal relationship between the lowell workers' public speeches and the strike's failure.

c.
there was a causal relationship between the lowell workers' strike and an increase in wages.

d.
there was a causal relationship between the lowell workers' protests and the factory cutting wages.