小丽同学在用天平、量筒、烧杯、水、细线测量石块的密度过程中，不小心损坏了量筒，请利用余下的器材把她测量石块的密度，写出必要的步骤和表达式．

As always, I am pleased to be here at the National Press Club for my (1) Speech. This is the seventh time I have had the (2) to give this speech, and over the years I have talked about a wide range of issues: (3) , reading, setting high expectations, improving the teaching profession, and (4) the American high school -- to name just a few.
I have just returned from a five-day, (5) tour of schools in rural America. We started in Monroe, Louisiana, and finished (6) later in Paducah, Kentucky. What I noticed most about the trip was the weather. Every time I (7) my Success Express School Bus, the local people who came to greet me (8) that the record for (9) had just been broken in their community. In each place, the temperature was always between (10) degrees.
Now, I have very good people on my staff. But the next time we plan a (11) , I’m going to have a (12) on my staff. I took this bus trip through rural America to make an important point that the (13) of children in our nation’s small towns cannot be ignored. Twenty-five percent of all our school children live in (14) all over America.
When it comes to our children, let’s always remember that children everywhere have (15) and (16) . Yet, schools in small towns too often have to (17) because of limited resources and a (18) . On my trip I put a p focus on the issues that matter in rural America, with a particular emphasis on (19) schools, reducing class size, and overcoming the (20) .