The teachers in middle school are very caring. Some teachers who often volunteer for blood donation make up lessons for students with learning difficulties for free. Every teacher who subsidizes poor students has formed difficult pairs with families with difficulties, but all those who make up for less None of the teachers had difficulties in pairing families. Based on the above premise, Which of the following items must be true. ["Some teachers who often volunteer blood don't support poor students.", 'Some teachers who sponsored poor students did not volunteer blood donations.', 'Some teachers who sponsor poor students often donate blood.', 'Some teachers who often volunteer for blood donation help with difficult families.']