Philosopher: It has been argued that because particular moral codes differ between cultures, morality must be entirely a product of culture and cannot be grounded in some universal human nature.
Conclusion
It's flawed to think that because moral codes differ, that the morality that gives birth to these codes is fabricated by one's culture, not rooted in one's human DNA.
Evidence
Some moral attitudes are shared across all cultures.
It's kind of analogous to food. There are universal tastes shared by all humans (like sweet and salty), but cultures differ when it comes to their cuisines.
The Blank
We usually see some Conclusion or Support indicator language right before the blank or at the beginning of the sentence. In this case, the rhetorical language is the wind-up for an Analogy.
So we know our job is to complete this analogy. The author's main agenda is saying that even though moral codes differ, morality might still be grounded in some universal nature.
She's using this analogy with food, so let's think about how the parts line up.
FOOD MORALITY each culture has each culture has the universal tastes certain shared of sweet & salty moral attitudes
these universal tastes provide the basis for ? ? ? many different cuisines
Goal
If we think about the author's overall conclusion that , then this analogy should be working its way back to talking about moral codes.
Moral codes are like cuisines (each culture's is different). Moral attitudes are like tastes (shared across all cultures).