Learn English – ”Through” or ”to”

Both sentences are appropriate, whether in spoken or written English, but they mean slightly different things.

1. Using remain indicates that the school is already closed and will continue to be closed until 7th June.

2. Using be indicates that from some unspecified time or date, the school will be closed until 7th June. It does not imply that the school is already closed.

Note that the word below in your question, which is a preposition, should come after two sentences rather than before. Alternatively, you might write: ..the following/next two sentences..

The process of acquiring infection can be described as:

1. Become infected (This exact Google search site:gov "become infected" gives 35,600 results and site:edu "become infected" 59,100 results.)

2. Get infected (This search site:gov "get infected" gives 13,600 results and site:edu "get infected" 12,500 results.)

"Be infected" is NOT used for acquiring but for having an infection.

I used "gov" and "edu" seraches because most results are from the largest online medical library pubmed.gov and university websites, which shows the actual usage of the terms in the medical world.