см. тж. представлять затруднения

• This process involves (or presents) (some) difficulties (or problems).

• Each new problem poses its own unique challenges.

• The location of new substations has been a problem because of space restrictions.

• The direct measurement of temperature behind the shock front still presents (or involves) severe difficulties.

• The study of an organism that cannot be readily maintained in the laboratory is fraught with great difficulties.

• Supplying power to a high-performance computer can be a major challenge.

см. тж. со временем

• Such experiments will become more precise and more numerous as time passes.

• Since all machines wear, their defects worsen as time goes on (or by).

• Such optical binaries (stars) can be distinguished from real couples only in the course of time.

• In (or With) time some of these bacteria developed metabolic pathways that led to ...

• As time elapses, the concentration profiles take on a different shape.

• Over the years the electronic micrometer instruments have become more and more automatic.

• The magnetic poles of the Earth tend to move slowly with the passage of time.

• These substances have accumulated through time.

• The pole of relative rotation can change its position through time.

• These properties vary with time.