"which will be challenging" is grammatically correct and can be used in written English.
This phrase is typically used to describe a situation, task, or activity that will be difficult or demanding. Here is an example: "I have decided to take on the new project at work, which will be challenging but also very rewarding."
Millar was road captain in Denmark and his experience will be crucial in the Olympic race which will be challenging to control.
The next step will be to test these ideas, which will be challenging as the mussels cannot be bred in the laboratory.
Thus, understanding of how phosphorylation of Ser23 and Ser24 in Lac1 and Lag1 stimulate ceramide synthase activity may require detailed structural information, which will be challenging to obtain for these polytopic integral membrane proteins.
Next we need a better plan for financing the health care law, which will be challenging because actually paying for federal programs (that is, increasing taxes) has become a no-go zone in Washington.
The company, which will be challenging formidable giants like eBay and Amazon.com, is the brainchild of Simon Rothman, who worked at eBay from 1999 to 2005 and was the primary creator and executive in charge of its automotive site, eBay Motors.
Critics say the law, which will be challenged at the supreme court on Monday, creates many single-parent families – especially women with small children – unable to take up full-time work because of childcare costs, and disproportionately affects people living outside London and the south-east, where salaries tend to be lower.
Ann Riley, 51, a library worker, who took part in the march, said: "There's grave concerns about the proposals which we don't feel have been particularly thought through there seems to be a lot of flaws in the proposals which we will be challenging".
So which films will be challenging The Avengers and The Dark Knight at the top of the superhero all-time box office charts?
De Blasio's plan has been criticized by The New York Times, which said it will be challenging for principals and administrators to add new services.
The broadcast has since inspired countless headlines, preoccupied pundits on Germany's ubiquitous television talk shows and may even become an issue in national elections this autumn in which left-leaning Social Democrats will be challenging the government coalition led by Chancellor Angela Merkel's conservative Christian Democrats.
Agreeing a set of goals that seek to end poverty, address social concerns and protect the environment, and to which all countries will commit to, will be challenging.
