Two currently popular virtual assistants are Google Assistant (Hey Google) and Siri (Apple). Alexa (Amazon) is also a widely used voice assistant.
Source: Applications of Natural Language Processing, chapter 6, section 6.2
The source passage lists three voice assistants as examples under "Voice assistants" in section 6.2 — Google Assistant, Alexa, and Siri. For a 1-mark question, naming any two is sufficient. Avoid over-explaining; just name them clearly.