Final answer:
The correct answer is option d) desincrustation. Desincrustation is the electrotherapy treatment used to break down sebum and liquefy blackheads, aiding in deep-pore cleansing.
Step-by-step explanation:
The electrotherapy treatment that can cause sebum to be broken down or blackheads to be liquefied, as in deep-pore cleansing, is desincrustation. This process involves the use of a mild electric current that breaks down the sebum. It is specifically designed to soften and emulsify sebum and keratin in the follicle, which makes it an effective treatment for cleansing pores and improving acne conditions. Therefore, the correct answer would be option d) desincrustation.