To solve this problem, we need to analyze each statement regarding ecological pyramids:$\newline \bullet$Option 1: Pyramid of biomass in sea is generally inverted.$\newline$ - In aquatic ecosystems, the pyramid of biomass is often inverted because the biomass of primary consumers (zooplankton) is greater than that of the producers (phytoplankton).$\newline$ - This is due to the high turnover rate of phytoplankton.$\newline$ - Therefore, this statement is correct.$\newline \bullet$Option 2: Pyramid of biomass in sea is generally upright.$\newline$ - As explained, the pyramid of biomass in aquatic ecosystems is typically inverted, not upright.$\newline$ - Therefore, this statement is not correct.$\newline \bullet$Option 3: Pyramid of energy is always upright.$\newline$ - The pyramid of energy is always upright because energy decreases at each trophic level due to the second law of thermodynamics.$\newline$ - Therefore, this statement is correct.$\newline \bullet$Option 4: Pyramid of numbers in a grassland ecosystem is upright.$\newline$ - In a grassland ecosystem, the pyramid of numbers is typically upright because the number of producers (grasses) is greater than the number of herbivores, which in turn is greater than the number of carnivores.$\newline$ - Therefore, this statement is correct.$\newline$Based on the analysis, the statement that is not correct is:$\newline$Option 2: Pyramid of biomass in sea is generally upright.$\newline$Thus, the correct option is Option 2.