Only logically similar parts of a sentence must be structurally similar (parallel).

There are several other issues with C:
a) efforts to is better idiomatically
b) ...continued rising and it reached... does not depict the cause and effect well; at least not as well as D does, using a participial phrase (...continued to rise, reaching...).

This was answered in another thread.
https://www.beatthegmat.com/defying-effo ... 99854.html

Just to elaborate on the cause-effect relationship that Ashish has mentioned about option C:
The 2 events - the USD defying policymakers' efforts to restrain it, the USD reaching the highest level in 6 years against the German mark - are not disconnected. The second is an outcome of the first.

'And' is a conjunction typically used to talk about 2 different ideas. Here, the ideas are not separate. Therefore, the use of 'and' is not appropriate here. This is the problem with option C, apart from the idiomatic issue.