The phrase 'focus of this activity' is correct and usable in written English.
You can use it when talking about the main aim of an activity or a project. For example, "The focus of this activity is to develop a plan for financial sustainability."
The stripy buzzing creatures are also the focus of this activity pack from the Bumblebee Conservation Trust.
The power of language in relation to LGBT rights is a key focus of this activity pack from Amnesty International.
Designing and modelling a 2D robotic arm is the focus of this activity from the Institution of Engineering and Technology (IET).
The focus of this activity is an unassuming brownstone on Tenth Street near Fifth Avenue in Greenwich Village that houses the Marshall Chess Club, the city's pre-eminent chess battleground.
Explain that because "coming-of-age" ceremonies like the one featured in this article are among the most common rites of passage in most societies around the world, they will serve as the focus of this activity.
Thus, the results showed that NAc lesions had a predominant effect on the amount of motor activity, whereas the predominant effects of DPAT were on a process related to the distribution or the focus of this activity.
Each item is asking the same question, but the focus of why this activity has not occurred is made explicit in the second of the questions whilst in the first it is assumed.
Recording and analysing sound signals is the focus of this whiteboard activity for secondary students.
Conceptually intertwined with the pathogenesis of SLE, the newly evolving topic of targeted therapy is the focus of this educational activity.
Police won't say what the focus of the activity is, she reports.
"The focus of the activity will be investigative enquiries and then recovery of the aircraft".
