The correct answer is: Only assumption II is implicit.
The statement “In case of any difficulty about this case, you may contact our company’s lawyer” implies that the company has a lawyer who is available to help with legal issues. However, it does not imply that every company has a lawyer, or that the company’s lawyer is thoroughly briefed about this particular case.
Assumption I is that each company has a lawyer of its own. This assumption is not necessary to support the statement, because the statement does not say that every company has a lawyer. For example, the company’s lawyer could be a consultant who is not employed by the company.
Assumption II is that the company’s lawyer is thoroughly briefed about this case. This assumption is necessary to support the statement, because the statement says that the company’s lawyer can help with legal issues about this case. If the company’s lawyer is not thoroughly briefed about the case, then he or she may not be able to help.
Therefore, only assumption II is implicit in the statement.