The correct answer is - C. negative as it threatens local biodiversity.
A new highly nutritious crop, if planted in an area where it has never been planted before, thus it is not native to that area, it practically means an introduction of an invasive species.
When it comes to the local biodiversity, this can have very negative effect for it, and that is because of two reasons:
1. The new crop, in order to be planted, requires arable land, and that land will be acquired by clearing up the space with the local species, thus destroying both the habitat of the species, and directly their numbers.
2. It will be an invasive species, and very often the invasive species are able to out-compete the native species, thus spreading around quickly and destroying them. Also, in this case, the situation will be that the invasive species will have human support, which will be even more devastating to the biodiversity.