Since the desert air was so dry the bread quickly turned stale . in this sentence which word serves as a clue that there is cause and effect

Since the desert air was so dry, the bread quickly turned stale.

I think that the word that serves as a clue is 'Since'. You could replace since with the word 'because' and the sentence would still make sense. The word 'since' shows the readers that because of something, something else happened. It is easy to see that there is cause and effect in this sentence.

I hope this helps :)

Explanation:

Classroom Size

Many areas of the country are facing classrooms that are literally busting out at the seams. A report at NEA Today two years ago discussed how schools in Georgia, in the midst of major funding cuts for schools, had no choice but to lift all class size limits to accommodate students with the faculty the school system could still afford to keep. More recently, Fairfax County in Virginia has been looking into a proposal to increase classroom sizes in the face of significant budget cuts. The Board of Education in South Carolina is also weighing their options in this area.

Poverty

Technorati reported last fall that 22 percent of the children in the U.S. live at or below poverty level. American Graduate defines poverty as a family of four with an annual income level of $23,050 or lower. American Graduate also cites a report from the Southern Education Foundation, which shows in 17 states across the U.S., low-income students now comprise the majority of public school students in those states. Some estimates put poverty levels for public school students at 25% in the not-so-distant future.

Family Factors

Family factors also play a role in a teacher’s ability to teach students. Principals and teachers agree that what is going on at home will impact a student’s propensity to learn. Divorce, single parents, poverty, violence and many other issues are all challenges a student brings to school every day. While some teachers and administrators try to work with children in less than ideal family environments, they can only do so much – especially when parents are often not willing to partner with the schools to provide for the children.