Which of the following guidelines are given in regards to intensity and frequency, to improve muscular strength? ( select those who apply )

workout sessions should be limited to twice a week for 15-30 minutes.
during each workout session, several different muscle groups should be worked.
exercises for each muscle group should include four to five sets of 10 to 15 repetitions each.
increase the weight only when you are able to complete three sets of 10 repetitions with ease.