LS正解.
补充一下,because接原因状语从句,becasue of接名词、代词或动名词,如because of doing sth.
e.g.Many living things lose their homes because people keep cutting down trees.
=Many living things lose their homes because of deforestation.
由于人们砍伐森林,很多生物都失去了他们的家园.
符号的话,由上可见不需要.