Judge the Following Sentence According to the Criteria Given Below

Judge the following sentence according to the criteria given below: "Upward intragenerational mobility is highly valued and promoted in Canada, considered by many as the "land of opportunity". This is a result of the degree of social mobility possible within an open stratification system".

A) The assertion is incorrect, but the reason is correct.
B) The assertion and the reason are both correct, but the reason is invalid.
C) The assertion is correct, but the reason is incorrect.
D) The assertion and the reason are both correct, and the reason is valid.