This question has two dimensions. It is an open question that seeks to understand what kind of design you admire, and it is also a question testing your knowledge of contemporary design. The best way to answer is to choose a landscape architect that is interesting and one that you know something about. It would also be helpful if you do genuinely like their work as this will allow you to speak passionately about it. Highlight why you admire them - consider their philosophical approach, a unified style they adopt, or innovations and contributions in the industry. A failure to be able to speak passionately and knowledgeably will indicate a lack of interest and awareness of the industry and leading professionals.