If a robot can alter its own trajectory in response to external conditions, it is considered to be:

Answer: Option B

If a robot has the capability to alter its own trajectory in response to external conditions, it is considered to be mobile.
Option A: "intelligent" is a broader term that encompasses various capabilities, including mobility, but it does not specifically refer to altering trajectory in response to external conditions.
Option C: "open loop" refers to a control system where the output is not affected by the current state of the system, which is not relevant to the scenario described.
Option D: "non-servo" refers to a type of control system where the output does not actively correct for errors, which is also not relevant to the scenario described.
Therefore, the correct choice for a robot that can alter its trajectory in response to external conditions is Option B: mobile.