The phrase "are presumably able" is correct and usable in written English.
It can be used when discussing someone's assumed capability or potential to do something based on available information or context.
Example: "Given their extensive training and experience, they are presumably able to handle the project without any issues."
Alternatives: "are likely capable" or "are expected to be able".
These young graduates who are chalking up parliamentary experience are presumably able to be there because they are parent-funded.
To ensure a sensitive and robust response to directional signals in complex and dynamic chemical landscapes, GCs are presumably able to amplify and filter external information.
But if someone knows that Washington is the capital of the United States, they are presumably able to express this knowledge in words.
However, some other owls, such as barn owls, short-eared owls (Asio flammeus) and even the related snowy owls have lower wing loading relative to their size and so are presumably able to fly faster, with more agility and for more extended periods than the Eurasian eagle-owl.
From this one can speculate that the complex process of revascularization in ischemic tissue is improved by the number of soluble factors present in the EPC-CM, which are presumably able to target simultaneously multiple cell types.
Therefore, assistance from local authorities who are presumably able to locate participants more efficiently and effectively than an outside researcher should be solicited.
Edgar was presumably able to draw on his experience of agitprop theatre of the 1960s and 70s, when companies such as Portable theatre would create and tour plays about contemporary issues (strikes, crimes, scandals).
MS-13 members called her in Kansas City, Mo., where United States marshals from the Witness Protection Program had her stashed away in a Marriott hotel, and were presumably able to persuade her to leave the program voluntarily.
Coca-Cola would not comment on the identity of its customers in North Korea, the people who were presumably able to taste that first batch of Coke, and this raised suspicions as to whether the drinks had reached ordinary North Koreans.
No Fleetwood Mac, as had been rumoured (ahem), but Arctic Monkeys and Mumford and Sons are eight very safe pairs of hands when it comes to headline slots, and the Rolling Stones, who Eavis was presumably able to afford using a Groupon voucher, do seem to represent a coup.
At the same time, hominins members of the human family lost those two particular bitter taste genes, so they were presumably able to eat a wider range of tuberous plants.
