Final answer:
Nonhuman primates involved in long-term language instruction have successfully displayed A) mastery of syntax, proficiency in written language, and development of regional dialects.
Step-by-step explanation:
The linguistic attributes that nonhuman primates involved in long-term language instruction have successfully displayed include mastery of syntax, proficiency in written language, and development of regional dialects.
Although nonhuman primates have limitations in learning human language, studies have shown that individuals of these species can learn and use basic vocabulary and simple word combinations to communicate their wants and needs. This demonstrates their ability to understand and use syntactic rules to create meaningful sentences.
Additionally, some nonhuman primates have been taught to use sign language or gestures as a form of written language. They have shown proficiency in using these symbolic systems to refer to objects and make comments or requests.
Furthermore, certain nonhuman primates have been observed to develop regional dialects within their groups, showing their ability to adapt and modify their vocalizations based on their social and environmental contexts.