What makes the documents provided to Sam and Alex unlawful?

The choice indicating that the documents contain blank spaces to be filled in after signing is considered unlawful because it compromises the integrity and legality of the document. The principle behind this practice is that all material terms of an agreement should be fully disclosed and agreed upon by all parties before a signature is obtained. If there are blank spaces, it allows for potential manipulation where one party could unilaterally fill in terms after the fact, which can lead to disputes and concerns regarding coercion or fraud.

In a real estate transaction or any binding agreement, ensuring that all details are clearly filled in and agreed upon prior to signing protects all parties involved and upholds trust in the documentation process. This makes the act of providing documents with blanks unacceptable under legal standards.

As for the other considerations, misleading information, missing required signatures, and exceeding document size limitations are also serious issues, but they do not directly point to the post-signing manipulation risk associated with blank spaces, which is why that option stands out in the context of the question.