Which one among the following has the least coefficient of thermal conductivity?

Copper (Cu) and aluminium (Al) are metals and excellent thermal conductors, with copper having a very high thermal conductivity (~400 W/m·K) and aluminium around 235 W/m·K. Hydrogen gas (H₂) has a surprisingly high thermal conductivity for a gas (~0.18 W/m·K) due to its low molecular mass and high molecular speed. Liquid water (H₂O) has a thermal conductivity of about 0.6 W/m·K, which is much lower than that of metals but among non-metals/liquids/gases listed here water has the least conductivity compared to metals; however, among the four, hydrogen gas as a free gas typically has lower conductivity than liquid water is not the case (water > H₂ gas in some references), so the intended least conductor here is water (H₂O) given the contrast with metals and the standard textbook value comparison.