A mother brings her 3- year- old daughter to the pediatrician b/c she "does not talk very much". Her vocabulary consists of only 10 words, and she speaks only one word at a time. Her past medical hx is notable for delays in developmental milestones: she walked independently at age 2, developed a pincer grasp at 15 months, and continues to have stranger anxiety. A hearing test completed in the clinic was normal. What is the likely diagnosis?

A. Autism spectrum disorder.
B. Global developmental delay.
C. Selective mutism.
D. Tic disorder.