Concept:
Sudden aphasia with right arm weakness suggests acute ischemic stroke, likely involving the dominant cerebral hemisphere. Evaluation of embolic source may require echocardiographic assessment, and TEE is useful for detecting cardiac and aortic arch sources of emboli.
Step 1: Identify neurological event.
Sudden onset aphasia and right arm weakness suggests:
\[
\text{Acute stroke}
\]
Step 2: Consider embolic source.
Cardioembolic causes are important in ischemic stroke evaluation.
Step 3: Choose indicated investigation from options.
Among the given options, the answer key indicates:
\[
\text{TEE}
\]
which can detect cardiac thrombus, valvular lesions, and other embolic sources.