Question 47: Which indexes will help with the performance of the following query?

Have a look at the following tables:

create table ggen
  select 1 as n union select 2 union select 3 union select 4 union
  select 5 union select 6 union select 7 union select 8 union
  select 9 union select 10;

create table g1tst
  select floor(rand()*10) + 1 as gtype,
  adddate('2010-01-01', interval rand()*360 day) as gdate,
  (rand()*1000000/100) as gsum
  from ggen a,ggen b,ggen c,ggen d,ggen e;

 
Which indexes will help with the performance of the following query?
(Find all correct answers)

select count(*)
  from g1tst v1,g1tst v2
  where v1.gdate=v2.gdate and v1.gtype=1 and v2.gtype=2;

+----------+
| count(*) |
+----------+
|   278397 |
+----------+
1 row in set (34.37 sec)

a) alter table g1tst add index (gdate,gtype);
b) alter table g1tst add index (gtype,gdate);
c) alter table g1tst add index (gtype);
d) alter table g1tst add index (gsum);
e) alter table g1tst add index (gdate);

 
[ Basic Optimizations (10%) - Using Indexes for Optimization ]