(A) Let-go current is the maximum current at which a person can still voluntarily release an energized conductor, so this statement is correct.
(B) Microshock occurs when extremely small currents (µA range) pass directly through the heart, making this statement true.
(C) ICU patients with invasive conductive leads (pacemaker wires, catheters, saline lines) are at high risk of microshock; hence true.
(D) Microshock safe current limits are in microamperes, not above 50 mA — so this statement is false.