The plane will arrive in ten minutes. (CORRECT)
All passengers are already on the board of the plane. (INCORRECT)
All passengers are already onboard the plane. (CORRECT)
All passengers are already on the plane. (CORRECT)
To swim across the river proved to be rather difficult than I expected. (INCORRECT)
To swim across the river proved to be more difficult than I expected. (CORRECT)
To swim across the river proved to be rather difficult. (CORRECT)
Almost every English word has a lot of meanings. (CORRECT)