Go instrument by instrument instead of statement by statement.
Gravimetric method: it is the oven-dry weighing method, the oldest and most direct way to know soil water content, so every other instrument gets checked against it. This supports (A) as true.
Resistance (gypsum) blocks: their electrical resistance changes with the ions dissolved in the soil water, so a saline soil confuses the reading regardless of actual moisture. That makes (B) false.
Neutron probe: it fires fast neutrons which lose energy mainly when they strike a nucleus of similar mass, which is the hydrogen nucleus in water molecules; the slowed neutron count is proportional to water content. Carbon has nothing to do with this, so (C) is false.
Tensiometer: it is a water filled tube with a porous cup, and it can only hold a vacuum reading over a narrow suction range before air enters the system, so it stops giving useful values in dry soil. So (D) is false.
Sprinkler moisture stations: placing sampling points between heads and a few metres from the lateral is exactly the standard recommended practice, so (E) is true.
\[\boxed{\text{(B), (C) and (D) are incorrect, option 2}}\]