I chose Saudi Arabia as the country. I need help answering the questions.

There are 25 elements found in living things. how many of these elements are found in some organisms but not all? 1 , 6 , 19 , 25

Donald is studying the eating habits of all students attending his school. he samples the population by dividing the students into groups by grade level and randomly selecting a proportionate number of students from each group. he then collects data from the sample. which type of sampling is used? select the correct answer below: systematic sampling convenience sampling stratified sampling cluster sampling

1. describe at least 3 similarities or differences between homo habilis and australopithecus 2. describe at least 3 similarities or differences between cro-magnon and neanderthals.