Answer:
1, 4 & 6 are likely to be correct
Explanation:
1 When the target group is American adults, who very often have landline telephones and cellphones, it can be argued that including them will be more accurate.
4 This may be true; I can imagine that there are people, socioeconomically different, who don´t have (access to) landline phones.
6. Birthday doesn´t have anything to do with age, as suggested in nr. 5 and nr. 7. Birthyear does. The selection of most recent birthday in a household is a good way of selecting at random.
2, 3 and 8 are statements that don´t have any scientifical reasoning.
