The correct option is
C Sieve tubes
Callose deposition has been described as a typical plant response to stress aimed at locally isolating the impact of the stress in the plant tissue through the deposition of a physical barrier. Callose is known to be deposited in sieve plates to seal sieve plate pores upon sieve tube severing, and even in response to low-intensity ultrasound which causes only minimal injury.
So, the correct answer is 'Sieve tubes'