lack something vs lack in something?
The sauce was lacking in flavor.
The sauce was lacking flavor.
Are both of these sentences correct? Do I have to put a preposition in?

Question

Answer

They're both correct, but they're grammatically different. It isn't simply a case of adding or omitting a preposition if you feel like it.  If 'lacking' is a verb, you don't use 'in'; if  'lacking' is an adjective, you do.

The sauce was lacking flavour =  The sauce lacked flavour.
Here, 'lack' here is a verb, and 'flavour' is the direct object.

The sauce was lacking in flavour.
Here, 'lacking' is a predicative adjective which requires a particular construction: 
be + lacking + in + indirect object

I hope that helps.

Answer

They're both correct! As another commenter already said, the preposition is correct but not nessecary.

Answer

Both are correct. No preposition is required but you can put it there if you like.

Answer

Both are correct. No preposition is required but you can put it there if you like.

No pierdas la oportunidad de aprender un idioma desde la comodidad de tu casa. ¡Explora nuestra selección de profesores de idiomas con experiencia e inscríbete ya en tu primera clase!