"must be attained" is a perfectly valid phrase to use in written English.
It can be used when you want to emphasize something that must be achieved or accomplished in order to progress. For example, "Success in life must be attained through hard work and dedication."
And this knowledge must be attained on its own terms.
Quotas " 'impose a fixed number or percentage which must be attained, or which cannot be exceeded,' " and "insulate the individual from comparison with all other candidates for the available seats".
And Zoe Barnes begins to exercise all the leverage she has to put Frank on notice that she does not belong to him, that there is a mutuality of interests that must be attained.
A review in Jazz Journal in December 1950 was condescending: "Before New Orleans music can be played, a complete relaxation and unself-consciousness, not normally an attribute of the white man, must be attained.
This completes our claim that optimality must be attained at the diagonal line.
However, unlike directly excited systems, parametric resonance has a minimum threshold amplitude that must be attained prior to its activation.
Consequently, TGF-β resistance must also be attained by other unknown mechanisms.
To do this, the initial dose and dose escalation, followed by the recommended dose and recommended dosing schedule must all be attained.
At larger sizes, tumours tend to spread to the trunk of the mice and cannot be sufficiently irradiated to achieve long term local tumour control; (b) Long term local tumour control must not be attained by fractionated radiotherapy alone.
Before peace can be attained, the blockade must be lifted, and occupation's walls, both visible and invisible, must come down.
If the goals with respect to user influence are to be attained, transport planning must be pursued with a greater understanding of how it conceives of its users as specific categories with particular needs and identities.
